Secret of Mana/Seiken Densetsu 2: I actually never played this before, a friend is insanely into it. I'd played the first Gameboy game in the series which was localized as Final Fantasy Adventure and it was a fun adventure RPG. This one...
Honestly, I can't stand the game. A lot of the music loops very quickly and feels subpar to a LOT of Square's other works. Seriously,
listen to "Ceremony" (edit, killed by copyright claim, here's another link:
https://www.youtube.com/watch?v=7zpMyoJ9Y_Q) and tell me you want to listen to it for multiple dungeons. I am aware it is supposed to be uncomfortable and discordant and grating, but ugh. On the whole, the first game in the series had a much preferable OST even though it was a Gameboy game.
The main sticking point is the combat system is horrendous and among the worst in any RPG I've played. Hit detection feels flaky and the game does a poor job of giving the player feedback if their attack hit or not, or if it "hit" but registered as a miss due to enemy stats. There's early enemies that can stunlock you to death by simply hitting you repeatedly as you have no small period of invulnerability when hit/knocked down, and for many enemies you can do the same to them (woe unto the foolish player who goes into the Haunted Forest before getting the game's second character). Getting all three party members help alleviate the stunlocking issue somewhat, though combat actually feels slower the further you get in the game as the emphasis on longer charge attacks and spells (which pause the game temporarily) increases. With physical attacks often whiffing due to enemies with i-frames, the charge attacks can actually be frustrating to release, since you can easily be interrupted out of them or they can simply whiff if the enemy does something to make themselves invulnerable. Spells eventually become the game breaker, and offensive spells are what you focus on spamming for bosses, which requires constantly reopening the menu and casting manually.
Spells automatically hit the target and cannot be dodged by moving away. This means that enemies with spells can essentially lock down your team with them. The first major spellcasting boss (the fire-themed one) will essentially rip you up if you used up all your MP prior to encountering it, since it constantly spams unavoidable spells and makes itself difficult to hit. It is the boss that teaches you to be prepared to spam your offensive spells on bosses as Freeze makes short work of an otherwise difficult boss.
The menu interface isn't much better and feels very awkward to navigate at times. You eventually get 3 party members, and while multiplayer is surprising to have in a SNES era RPG, the entire experience feels unpleasant, with combat that doesn't feel like your hits connect reliably, which is due to enemies often having iframes when casting, and poor feedback when attacks actually register, what your charge attack hitboxes are, etc. The story is also atrocious and the plot proceeds at an absolutely breakneck pace with no character development whatsoever and frankly poor writing. There are more enjoyable single player experiences to be had in overhead-style RPGs for the SNES. Brain Lord for instance offers a vastly more enjoyable experience with far more engaging combat (and has many of the same weapon types to use with far better script writing/dungeons/magic system).
Surprisingly enough one thing I don't fault is the AI - it's surprisingly reliable at keeping enemies stunlocked with some weapons like the Javelin, though when it's allowed to use charge attacks it often whiffs them. Charge attacks go up to a whopping level 8, and while they look nifty, it really makes the combat pacing feel slow when you're encouraged to max charge attacks to deal real damage while another character does stunlocking to give you time to charge.
If I want a real-time RPG experience, I want it to feel like combat is responsive. There are better multiplayer RPGs and dungeon crawlers that scratch my real time combat RPG itch than this does, especially when the main threat (spells) cannot be reliably dodged. It reminds me of the very first Tales game for the SNES with the constant pausing for spells, though Tales of Phantasia's combat still feels like hits connect more "solidly". The later Tales of games are much more enjoyable when they got away from spells pausing combat and becoming actually dodgeable attacks in Tales of Eternia.
edit: apparently the melee whiffing thing is because enemies randomly go into either a staggered or a knockdown animation when hit, and one of them lets you do melee hits which will connect after the animation's done, and the other simply won't, it's weird and janky, Tales of Phantasia for SNES feels much faster and better in the endgame where Cless + Chester minimize how often the screen's pausing for spells (which the AI will helpfully cast aggressively or not at all depending on how you set their tactics), whereas in Secret of Mana you basically want to spam the Sprite's offensive spells non-stop late game, and the lack of a button shortcut to do it is tediously inconvenient...