For me... it's between three:
VI-- I loved the characters in this one. Also the music. I've never beaten it yet.

IX-- This one is the best. Unbeatable Final Fantasy, Characters (Like Aadria said), and everything else. This... Was my first FF. I have not beaten it either xD

XII-- Stop bashing on this game! It's a great game, and is a close third in my book. the battle system was... Different. Some characters were well done, some... Not. TONS of weapons, and Quickenings were fun to watch. I like the liscenses, and how you could give anyone, any weapon. I specialized Ashe (My favorite XII character) in great swords. She is weilding a claymore right now ^^'.

Enough talking! I need to shut up.

Love JillXWesker