There are way too many fantastic RPGs to pick just one on from just the PS1
Final Fantasy Tactics, Saga Frontier, Legend of Mana, Front Mission 3, Breath of Fire 3, Castlevania: Symphony of the Night, Wild Arms 2, Star Ocean 2, Threads of Fate, Jade Cacoon, Parasite Eve, Azure Dreams, Guardian's Crusade, Tales of Destiny 2, Legend of Dragoon, Chocobo's Dungeon, Grandia, etc.
Throw in SNES, PS2, PSP, and PC libraries and you will be sifting for weeks trying to figure out which one seems better than the other, but they are all so different... so on and so forth.
I do think I would be amazing if a developer took the best elements from Castlevania: Symphony of the Night, Ragnarok Online, and Torchlight 2 and made the best RPG ever imaginable! :D
