I liked Space Invaders Infinity Gene on 360 as well. The mobile versions dont have the last few worlds where the game goes into 3D shapes and raycrisis & treasure style patterns. Was one of the first 1CCs I got but I dunno if I'd recommend that since it's painfully long.
That vote sounds fun, we had similar ones for doujin games and soundtracks over the years.
A few games I didn't see mentioned. Almost all are untraditional shmups though:
Kaikan
RefRain ~prism memories~
Sora
2010 Sequel to Suguri. These games focus on special dashing mechanic used to dodge basic projectiles and graze to gain attack meter. Lock-on system and technical weapon use. Sora takes it further with polished presentation, more weapons and crazy enemy patterns.
Hard to describe this game, maybe watch jaimers' run for an idea.
Ginga Force
Third shmup by Qute following Judgement Silversword & Eschatos. Untraditional per-stage score attack game. Stages usually have some unique gimmick or extended boss fight. Ridiculous/fun bullet patterns on hard mode. Focus on bullet cancels and some tactical suicides. Here's to hoping Natsuki Chronicle coming out right at the end of the decade is really good too.
Murasaki & Murasaki Tsurugi
Shmup / puzzle hybrid with unique method of attacking enemies by shooting special blocks into eachother causing chain reactions. Boss fights with some pretty clever / fun to dodge patterns. Have to rethink movement because of the puzzle mechanics angle element. Some challenging dodging in both games in their hardest stages. Series has strong soundtracks and a unique visual style.
Assault Android Cactus
2015 Arena shooter that beats out Nex Machina in most aspects for me. Good stage variety and full chaining them is a great challenge. Many characters to choose from with different normal shots and special weapons. Hard mode added for free in 2019 revamps the stages and is really challenging to S+ rank even for veterans of the genre.
Solid scoring system even by general shmup standards: fairly lenient donpachi style chaining, but killing enemies at once gives a temporary 'burst' to multiplier a bit like esprade. Big time bonus scaled to fit each stage.
'Semi-random' enemy spawn and powerup system that seems to work for both people looking for randomness and hardcore play: enemy spawns are based on your rough location, and powerups are on a global timer. So if executing a solid route the same things happen. If not, the variation on diverging from route is predictable.
I might rate Nex Machina higher if game long chaining and secret hunting appealed to me at all. AAC feels like a great pick up and play score attack game for individual stages. Also less reliance on an evasive / invincible dodge move and more normal shmup dodging.
Rival Megagun
New versus shooter akin to Twinkle Star Sprites and PoDD&PoFV. More focus on normal shmup gameplay & bullet hell dodging than TSS. Playing on the higher difficulties and in longer matches the enemy patterns get seriously intense, for most stages in a way that still feels like solid shmup stage design.
I'm not sure what the general consensus is on this, haven't seen anyone into this subgenre (TSS, POFV etc.) say anything negative about the game. The upcoming EXA arcade release will probably come with some gameplay revamps and further tweaks. Largest playerbase is in japan on PC. Netcode is extremely good, the normal shmup part is lagless. Input delay only happens when controlling the boss form; in which case it may be for the best those moves have some base control delay. Assuming not that many people have given this a shot yet, but the japanese group is keeping it alive with weekly sessions.
And yeah, even Alltynex Second came out in 2010. I don't really see a shortage here. Personally still havent spent much time with Crimzon Clover. That and many others like Stellavanity you could already spend years on.