I & II: I like the Playstation Origins version best. The NES versions don't have auto targeting, which may frustrate those that have only played later games (or people like me that hate "ineffective" attacks). The Game Boy versions seem too easy for my liking. Origins is balanced just right for me.

III: I suggest the NES version. The DS version makes certain dungeons too easy (Cave of Shadows comes to mind) and I'd rather have Capacity points limit job changes than a temporary stat penalty.

IV: I play the Playstation version, but any version other than SNES is good. The SNES game is missing a command I like to use. It's also not much of a challenge.

V: I've only played the Playstation version, and the translation is horrible.

VI: Play any version. They're all good.