I favorite in order are likely: IX, T, VII, VI, CC, XII, VIII.
As the only real controversial item here that might need some context. I recognize that Crystal Chronicles (The original, none of this newer stuff) is here or there, but I have a lot of siblings and had 4 real cheap GBAs so I always had people to play it with. I also liked its style, sound, and general story. That game ended up defining my idea of adventure a lot.
VIII I also do not recognize as a "good" final fantasy. But I like it, it has just enough weird stuff and silly magic junctioning and highschool superhero military melodrama for me to be amused. The love story is the worst in FF, the music is only occasionally as good as the others. (13, Worse than 14, at least has a better love story than 8 strangely enough, VanilleXFang seems to be a pretty strong case. They talked to each other at least once. More chemistry then Squall and Rinoa had.