This Japanese wiki contains a list of a large amount of arcade STGs ranked by difficulty on a scale of 0 to 50.
The games are sorted by loop clears and such. Some of the hardest are a 2-ALL of DOJWL, an Ura 2-ALL of Ketsui and a 2-ALL of Sengoku Blade. Some games have explanations (in Japanese) if you click on their title.
The easiest games are mainly just staying in a certain place such as Night Raid which involves staying in the top left corner, although Raiden Fighters 2 with the Fairy is pretty low (some factors increase or decrease the rating, i.e. autofire in Darius Gaiden). Deathsmiles II is the easiest Cave game (5) and Deathsmiles is the second easiest (9). I wonder why Nemesis is a lot lower than its Japanese counterpart Gradius? Perhaps due to the recovery enemies?
This is a pretty good resource (despite being in Japanese) and I think the community should be more aware of it!
vvv_stg translated the list into English. [Mod edit: moved to first post and removed spoiler tag so this list is easier to find]
vvv_stg wrote:Tried translating the list into English. I should have realized that this list has ~300 entries before trying to do that. I've not done much proofreading so far, and it has quite a few places where specific games left me confused (marked with question marks). Plus I still have very vague idea what section headings are trying to say. But what I have so far might be useful, so here it is:
Japanese difficulty index ## Title Goal Notes 45 Dodonpachi Daioujou WL [CAVE, 2002] 2-ALL -3 for International version 44 Mushihimesama Futari [CAVE, 2006] Ultra Ver. 1.5, Abnormal palm Parodius Da! [Konami, 1990] 2-ALL Detana!! Twinbee [Konami, 1991] 2-ALL 43 Ketsui [CAVE, 2003] 2-ALL Ura +1 for using Tiger Schwert Argus [NMK, 1986] 1-ALL Omega Fighter [UPL, 1989] 2-ALL Game Tengoku [Jaleco, 1995] 2-ALL with autofire 42 Mushihimesama [CAVE, 2004] Ultra Sengoku Blade [Psikyo, 1996] 2-ALL with A autofire Valtric [NMK, 1986] 1-ALL [Area 1-4] 41 Twin Eagle [Seta, 1988] ALL 40 Strikers 1945 [Psikyo, 1995] 2-ALL BF-109・P-51 Xexex [Konami, 1991] 2-ALL Mystic Riders / Gun Hohki [Irem, 1992] 2-ALL Shienryu [Warashi, 1997] 2-ALL Vasara 2 [VISCO, 2001] 天の巻[2-ALL] +3 with Takeda Nobukatsu 39 Dodonpachi [CAVE, 1997] 2-ALL Strikers 1945 II [Psikyo, 1997] 2-ALL Flying Pancake Gunbird 2 [Psikyo, 1998] 2-ALL Pistol Daimyo no Bōken [Namco, 1990] Hardest route P-47 Aces [NMK, 1995] ALL without autofire; -2 with it 38 Progear no Arashi [CAVE, 2001] 2-ALL Gunbird [Psikyo, 1994] 2-ALL 37 Dodonpachi Daioujou BL [CAVE, 2002] 2-ALL Deathsmiles MBL [CAVE, 2007] LV999 [?] +2 for Canyon; +4 for TLB Dragon Blaze [Psikyo, 2000] 2-ALL Zero Gunner 2 [Psikyo, 2001] 2-ALL Mahou Daisakusen [Raizing, 1993] 2-ALL 36 Ketsui [CAVE, 2003] 2-ALL Omote Strikers 1999 [Psikyo, 1999] 2-ALL with X-36; +4 with other ships Image Fight [Irem, 1989] 2-ALL no 補習, autofire; +8 for loop 2 penalty areas Daioh [Athena, 1993] 2-ALL R-Type 2 [Irem, 1989] 2-ALL no autofire; -2 for autofire; -2 for International version Viper Phase 1 [old ver.] [Seibu, 1995] ALL no autofire; -6 for autofire Mushihimesama Futari BL [CAVE, 2007] God mode Reco; -6 if no TLB 35 Battle Garegga [Raizing, 1996] Harder +1 for extended two-loop version Dodonpachi Daifukkatsu BL [CAVE, 2008] with TLB [???] no autobomb; strong style only Strikers 1945 Plus [Psikyo, 1999] 2-ALL with Pancake Space Battleship Gomora [UPL, 1990] with autofire 34 Ikaruga [Treasure, 2001] Hard Raiden IV [MOSS, 2007] 2-ALL Zing Zing Zip [Allumer, 1992] 1-ALL as 1P; with autofire Battlantis [Konami, 1987] 2-ALL 33 Donpachi [CAVE, 1995] 2-ALL -3 for US version; +2 for Hong Kong version Crimzon Clover [NESiCA] [Yotsubane, 2013] Unlimited using Type-Z Raiden DX [Seibu, 1994] Practice course, 1-8 with C autofire USAAF Mustang [NMK, 1990] 1-ALL no autofire; -8 for autofire 32 Trigon [Konami, 1990] 2-ALL with autofire V-V [Toaplan, 1993] 2-ALL P-47 [NMK, 1988] 1-ALL no autofire; -5 for autofire 31 Dodonpachi Daifukkatsu [CAVE, 2008] 2-ALL Ura [Strong Style] Ver. 1.5; +4 for Bomb style; +12 for Power style Dodonpachi Saidaioujou [CAVE, 2012] ALL via Hibachi -11 without Hibachi Thunder Dragon [NMK, 1991] 1-ALL without autofire; -1 with it 30 Dangun Feveron [CAVE, 1998] ALL via TLB -2 if no TLB; +11 if playing as Uotaro RayStorm [Taito, 1996] ALL Gradius III [Konami, 1989] 1-ALL with autofire; weapon type B [+2 for A, +4 for C, +1 for D]; +2 for 2-ALL; +13 for 3-ALL and further Raiden II [Seibu, 1993] 1-ALL with autofire; +5 without it; -1 for international version 29 R-Type [Irem, 1987] 2-ALL without autofire; -3 with it Omega Fighter [UPL, 1989] 1-ALL 28 Dodonpachi Daifukkatsu BL [CAVE, 2008] Bomb style, via Hibachi +1 for Power style, +5 for Strong style Thunder Dragon 2 [NMK, 1993] ALL 2P or 1P with autofire; +6 for 1P without autofire Ultra Guard [?] [Seta/Banpresto, 1996] ALL without autofire Deathsmiles [CAVE, 2007] ALL via Extra [LV3] -9 without Extra 27 1944: The Loop Master [8ing, 2000] ALL [1-loop mode] Shippu Mahou Daisakusen [Raizing, 1994] 2-ALL Sonic Wings [Video System, 1992] 2-ALL with AJ-37 or IDS; +4 for F-18 or FSX 1943 [Capcom, 1987] ALL [vs. Yamato] without autofire; -8 with it Viper Phase 1 [new ver.] [Seibu, 1996] ALL without autofire; -3 with it Strike Gunner S.T.G [Athena, 1991] ALL without autofire; -5 with it 26 Battle Garegga [Raizing, 1996] ALL [1-loop mode] with Golden Bat Thunder Blaster [Irem, 1991] ALL without autofire; -20 with it Flak Attack [Konami, 1987] 2-ALL X-Multiply [Irem, 1989] 2-ALL with autofire Rezon [Allumer, 1991] ALL Acrobat Mission [UPL, 1991] ALL Nostradamus [FACE, 1993] 2P side; with autofire 25 Armed Police Batrider [Raizing, 1998] Advanced course [stage 7 route] [?] Sokyugurentai [Raizing, 1996] ALL with Toryu Shienryu [Warashi, 1997] 1-ALL Space Bomber [Psikyo, 1998] ALL Ver. B Sexy Parodius [Konami, 1996] ALL via Special stage autofire; -10 if no special stage Saint Dragon [NMK, 1989] ALL Radiant Silvergun [Treasure, 1998] ALL [Stage 4 route] Mars Matrix [Takumi, 2000] ALL 24 Batsugun Special Version [Toaplan, 1994] 4-ALL with C autofire; +5 with C-type Salamander 2 [Konami, 1995] 2-ALL with autofire Raiden [Seibu, 1990] 1-ALL with autofire; +2 without it Same! Same! Same! [Toaplan, 1989] 1-ALL without autofire; -10 with it; -10 for international version Ibara [CAVE, 2005] ALL 1P side Muchi Muchi Pork! [CAVE, 2007] 1-ALL Sengoku Ace [Psikyo, 1993] 2-ALL with Aine; +7 with Kenoumaru Darius II [Taito, 1989] ALL without autofire; -10 with it Parodius Da! [Konami, 1990] 1-ALL with autofire War of Aero [Allumer, 1993] 2-ALL with autofire Gunbird 2 [Psikyo, 1998] 1-ALL Sengoku Blade [Psikyo, 1996] 1-ALL Raiden DX [Seibu, 1994] Practice course, 1-5 with C autofire Daioh [Athena, 1993] 1-ALL -1 for US version Air Duel [Irem, 1990] 1-ALL without autofire Battlantis [Konami, 1987] 1-ALL +2 for International version Kyukyoku Tiger [Toaplan, 1987] 1-ALL without autofire; -10 with it; -13 for international version Operation Ragnarok [NMK, 1994] ALL without autofire; -4 with it Blazing Star [Yumekobo, 1998] ALL without autofire; -1 with it Dogyuun [Toaplan, 1992] 1-ALL without autofire; -2 with it Mazinger Z [Banpresto, 1994] 2-ALL without autofire; -2 with it 23 Dodonpachi Daifukkatsu [CAVE, 2008] Omote 2-ALL [Strong style] Ver. 1.5; +2 for Bomb style; +6 for Power style Mushihimesama Futari [CAVE, 2006] Maniac Ver. 1.5 E.D.F. [Jaleco, 1991] ALL Under Defeat [G. Rev, 2005] 2-ALL Gokujou Parodius [Konami, 1994] ALL via Special stage with autofire; -10 if no Special stage Gradius IV [Konami, 1998] 1-ALL Equipment 5; +1 for 1, +2 for 2 or 6, +4 for 3 Raiden III [MOSS, 2005] ALL RayForce [Taito, 1993] ALL Great Mahou Daisakusen [Raizing, 2000] ALL [1-loop mode] with Birthday In the Hunt [Irem, 1993] ALL Chariot [Wonder 3] [Capcom, 1991] ALL without autofire Twin Hawk [Toaplan, 1989] 1-ALL without autofire; -10 with it; -8 for International version [-15 with autofire] 22 Dodonpachi Daioujou WL [CAVE, 2002] 1-ALL Crimzon Clover [NESiCA] [Yotsubane, 2013] Original with Type-Z Espgaluda II [CAVE, 2005] ALL +4 for Shin Seseri Radiant Silvergun [Treasure, 1998] ALL [Stage 2 route] Giga Wing 2 [Takumi, 2000] ALL with TLB Battle Bakraid [Raizing, 1999] Advanced course with F-111B Dragon Blaze [Psikyo, 2000] 1-ALL 21 Ketsui [CAVE, 2003] 1-ALL [Tiger Schwert] Strikers 1945 II [Psikyo, 1997] 1-ALL with Hayate Dodonpachi II [IGS, 2001] with TLB [I.R.] Castle Shikigami [Alfa System, 2001] ALL Ikaruga [Treasure, 2001] Normal Blazeon [Irem, 1992] ALL with autofire; +10 without it Raiden DX [Seibu, 1994] Expert 1-ALL without 9th stage; with C autofire Vasara 2 [VISCO, 2001] 天の巻[1-ALL] Sonic Wings 3 [Video System, 1995] 2-ALL using P61; with autofire 20 Dodonpachi Daioujou BL [CAVE, 2002] 1-ALL +8 for Hibachi Esprade [CAVE, 1998] ALL Trouble Witches AC [Studio Siesta, 2009] ALL Homura [Taito, 2005] ALL Trigon [Konami, 1990] 1-ALL Guwange [CAVE, 1999] ALL Zero Gunner 2 [Psikyo, 2001] 1-ALL Castle Shikigami 3 [Alfa System, 2006] ALL with Nagino Strikers 1945 [Psikyo, 1995] 1-ALL Strikers 1999 [Psikyo, 1999] 1-ALL Strikers 1945 Plus [Psikyo, 1999] 1-ALL GigaWing Generations [Takumi, 2004] ALL with TLB Radirgy [Milestone, 2005] Laser Tatsujin [Toaplan, 1988] 1-ALL without autofire; -7 with it Metal Hawk [Namco, 1988] ALL Ryujin [East Technology, 1993] ALL ignoring power items V-V [Toaplan, 1993] 1-ALL Bomb mode; -2 for international version 19XX [Capcom, 1996] ALL with or without autofire 19 G-Darius Ver. 2 [Taito, 1997] ALL Raiden IV [MOSS, 2007] 1-ALL ORIGINAL Air Gallet [Gazelle, 1996] ALL Psyvariar 2 [SKONEC, 2003] ALL [no TLB] +13 with TLB Psyvariar Revision [SKONEC, 2000] ALL [X-A] +12 with TLB radirgy noa [Milestone, 2009] +1 for true ending R-Type II [Irem, 1989] 1-ALL Double Wings [Mitchell, 1993] 1-ALL 18 Mushihimesama [CAVE, 2004] Maniac Crimzon Clover [NESiCA] [Yotsubane, 2013] Boost Progear no Arashi [CAVE, 2001] 1-ALL A-Jax [Konami, 1987] ALL War of Aero [Allumer, 1993] 1-ALL Sonic Wings 2 [Video System, 1994] 1-ALL Heavy Unit [Kaneko, 1988] 1-ALL with autofire R-Type [Irem, 1987] 1-ALL Fixeight [Toaplan, 1992] 1-ALL Image Fight [Irem, 1989] 1-ALL without penalty area; with autofire Giga Wing [Takumi, 1999] ALL [true ending] true ending [no continues] Mahou Daisakusen [Raizing, 1993] 1-ALL -5 for international version 17 Mushihimesama Futari BL [CAVE, 2007] Maniac Dodonpachi [CAVE, 1997] 1-ALL Gunbird [Psikyo, 1994] 1-ALL Detana!! Twinbee [Konami, 1991] 1-ALL Vasara [VISCO, 2000] ALL Super Dimension Fortress Macross [NMK, 1992] 2-ALL with autofire Air Buster [Kaneko, 1990] Darius Gaiden [Taito, 1994] Survival route no autofire; -10 with it 16 Donpachi [CAVE, 1995] 1-ALL Mushihimesama Futari [CAVE, 2006] Original Ver. 1.5 Espgaluda [CAVE, 2003] ALL Sol Divide [Psikyo, 1997] 1-ALL Hishouzame [Toaplan, 1987] 1-ALL Sonic Wings [Video System, 1992] 1-ALL RayCrisis [Taito, 1998] ALL with WR-03 Out Zone [Toaplan, 1990] 1-ALL Fighting Hawk [Taito, 1989] ALL Dragon Spirit [Namco, 1987] ALL without autofire; -10 with it Gunnail [NMK, 1993] ALL with autofire; +1 without it 1945k III [Promat, 2000] with Su-37 or Se-11L without exploiting bugs Stagger 1 [Afega, 1998] with Red Hawk without autofire 15 Dodonpachi Daifukkatsu BL [CAVE, 2008] without Hibachi, Bomb style Mushihimesama [CAVE, 2004] Original Guardian Force [SUCCESS, 1998] ALL Pink Sweets [CAVE, 2006] ALL with infinite lives trick Gun Frontier [Taito, 1990] ALL with autofire Galaga 88 [Namco, 1987] ALL Game Tengoku [Jaleco, 1995] 1-ALL with autofire Darius [Taito, 1986] ALL [?]; +1 for EX plus alpha [Jaleco, 1989] 1-ALL without autofire Border Down [G. Rev, 2003] ALL [6A] +3 for B and D; +2 for C Under Defeat [G. Rev, 2005] 1-ALL R-Type Leo [Irem, 1992] ALL X-Multiply [Irem, 1989] 1-ALL with autofire Zero Wing [Toaplan, 1989] 1-ALL +4 for no autofire; +7 for 2-ALL; +30 for 3-ALL and higher; -3 for international version Mystic Riders / Gun Hohki [Irem, 1992] 1-ALL Terra Cresta [Nichibutsu, 1985] 1-ALL 14 Dariusburst AC EX [Taito, 2011] ALL [route QUZ] Sand Scorpion [FACE/Sankindou, 1992] 1-ALL with autofire G-Darius [Taito, 1997] ALL [zone U] with autofire Shippu Mahou Daisakusen [Raizing, 1994] 1-ALL Xexex [Konami, 1991] 1-ALL +6 for international version Thunder Force AC [Technosoft, 1990] ALL without autofire; -4 with it Viewpoint [SNK, 1992] ALL 13 Mushihimesama Futari BL [CAVE, 2007] Original Space Bomber [Psikyo, 1998] ALL Ver. B played as tetris block Akai Katana [CAVE, 2010] ALL Ikaruga [Treasure, 2001] Easy TwinBee [Konami, 1985] 1-ALL [5 stages] ignoring power items Carrier Air Wing [Capcom, 1990] ALL without autofire; -5 with it Sonic Wings 3 [Video System, 1995] 1-ALL using P61; with autofire Raiden DX [Seibu, 1994] Novice with C autofire 12 Dodonpachi Daifukkatsu [CAVE, 2008] 1-ALL [Strong style] Ver. 1.5; +2 for Bomb style; +5 for Power style Raiden IV [MOSS, 2007] LIGHT Batsugun [Toaplan, 1994] ALL Xevious [Namco, 1982] 1-ALL Dragon Saber [Namco, 1990] ALL Triggerheart Exelica [Warashi, 2006] Strato Fighter [Tecmo, 1990] 2-ALL Side Arms [Capcom, 1986] ALL without autofire Sengoku Ace [Psikyo, 1993] 1-ALL with Aine Metal Black [Taito, 1991] ALL without autofire; -5 with it Area 88 [Capcom, 1989] ALL without autofire; -5 with it Tank Force [Namco, 1991] ALL 11 Salamander 2 [Konami, 1995] 1-ALL with autofire Castle Shikigami 2 [Alfa System, 2003] ALL with Kim Rapid Hero [NMK, 1994] ALL with autofire TwinBee Yahho! [Konami, 1995] 1-ALL Gradius II [Konami, 1988] 1-ALL [weapon type 4] with autofire; +1 for type 3; +2 for type 1 or type 2 Section Z [Capcom, 1985] 1-ALL Thundercade [Taito, 1987] ALL without autofire; -6 with it 10 Dariusburst AC [Taito, 2010] ALL [route CGL] [?] 1941 [Capcom, 1990] ALL with autofire Gradius [Konami, 1985] 1-ALL Ordyne [Namco, 1988] ALL Phelios [Namco, 1988] ALL with autofire Megablast [Taito, 1989] ALL with autofire 9 Deathsmiles [CAVE, 2007] No Canyon Mazinger Z [Banpresto, 1994] 1-ALL Last Resort [SNK, 1992] 2-ALL with autofire Raiden Fighters JET [Seibu, 1998] ALL3 [with TLB] with Fairy; +5 with Slave; +15 to +20 for others Salamander [Konami, 1986] 1-ALL with autofire 8 Thunder Cross II [Konami, 1991] 1-ALL Life Force [Konami, 1987] 1-ALL 2P side; +1 for 1P Super Dimension Fortress Macross [NMK, 1992] 1-ALL Cloud Master [Taito, 1988] ALL The Last Day [Dooyong, 1990] 1-ALL without autofire; -4 with it Raiden Fighters [Seibu, 1996] ALL as Slave; +10 to +16 with others 7 Thunder Cross [Konami, 1988] 1-ALL with autofire; +11 for international version 1943 Kai [Capcom, 1987] ALL [vs. Yamato] -5 for Shotgun Cosmo Gang the Video [Namco, 1991] 1-ALL Final Star Force [Tecmo, 1992] ALL 6 Dariusburst AC EX [Taito, 2011] ALL [route ORV] [?] Kyukyoku Tiger II [Takumi, 1996] ALL 1P side; +5 as 2P 5 Dariusburst AC [Taito, 2010] ALL [route ADH] [?] Deathsmiles II [CAVE, 2009] Survival route Fantasy Zone [Sega, 1986] ALL autofire Twinkle Star Sprites [ADK, 1996] ALL Dragon Breed [Irem, 1989] 1-ALL Raiden DX [Seibu, 1994] Practice course using radar shot [?]; with C autofire Strato Fighter [Tecmo, 1990] 1-ALL without autofire; -3 with it 4 Prehistoric Isle 2 [Yumekobo, 1999] ALL -1 with autofire Terra Force [Nichibutsu, 1987] 1-ALL Nemesis [Konami, 1985] 1-ALL Captain Tomaday [VISCO, 1999] ALL 3 Gekirindan [Taito, 1995] ALL 2P side Insector X [Taito, 1989] Advanced course Batsugun Special Version [Toaplan, 1994] 1-ALL Storm Blade [VISCO, 1996] 1-ALL Vimana [Toaplan, 1991] 1-ALL +2 without autofire Slap Fight [Toaplan, 1996] 1-ALL [Area 100] 2 Raiden Fighters 2 [Seibu, 1997] ALL [with TLB] with Fairy; +2 with Slave; +18 to +22 with others Asuka and Asuka [VISCO, 1988] ALL Fire Barrel [Irem, 1993] 1-ALL with autofire; +4 for 3-ALL 1 Night Raid [Takumi, 2001] ALL by staying in upper left corner; +22 without it 0 Karous [Milestone, 2006] Easy
