Final Fantasy VI is my favorite for many reasons:
1 - no central main character, almost ALL of them are deep and well developed.
2 - LOTS of different characters with distinct play styles, equipment loadouts, weapons, skills, etc
3 - Best villain in a game, ever
4 - LOADS of sidequests. in fact the entire second half of the game is nonlinear and optional
5 - Fantastic story with loads of twists and turns, reveals, and shifting allegiences.
6 - Maybe the best score in a FF game...but it's got some persistently good competition from many others
I just think it's so fresh compared to the others, with less linearity, optional characters/events, and oh my god Kefka is such a memorable villain. who cares if he's loosely based off The Joker, it's fantastic, maniacal, and successful! there were so many little nuances and quirks to the game (like killing doomtrain with a phoenix down) as well as high concepts like going into Cyan's mind to confront and defeat his demons. To this day I haven't unlocked everything or figured everything out.
My Console Library:
PS5, Switch, XSX
PS4, PS3, PS2, PS1, WiiU, Wii, GCN, N64 SNES, XBO, 360
3DS, DS, GBA, Vita, PSP, Android