FF1, best Final Fantasy ever. Now if only they made the GBA version harder so that I didn't skip so marrily along in the game. Heart of Chaos dungeons, so kickass though.
I tend to prefer Fighter, Fighter, Red Mage, Red Mage. Past that though, I've also done solo everyone runs in the original except for Black Mage and White Mage, which it turns out I'm not leet enough to pull off. Oh well.
FFTA, fun game, but oh so painfully easy to break. Though my favorite character was a human paladin/fighter with dual wielding that killed just about any boss in a single blow. Epic.
Other than FFT, FFTA, and FF1, can't say I enjoy the Final Fantasy series too much. FF6 I enjoyed for the first half, but then the second half just seemed to be stringed together parts that felt... rushed? Unconnected? I don't know, FF6 just got old after the world hit armageddon.