Quick impromptu list, so if you ask again tomorrow I might have a different answer:

Games:

#1: VIII
#2: XIV
#3: XII
#4: VII
#5: IX

Characters:

Seifer, Barrett, Tifa, Minfilia

Spinoff: Crystal Chronicles (freaking love the hell out of this game)

Final Fantasy X  -  Maester Seymour

Favorite FF is kind of a tie between VI and VII. I tend to have the categories, pre-3D VI, post-3D VII.

Thus my favorite 2 characters are Locke (VI) and Cloud (VII).

Least favorite post-3D is FFIX. It so deviated by the progression of FF I feel like it should have been an offshoot or something not labeled FF. I just didn't like it and to this day is my least played FF. I like FFXV _more_ which should tell you how bad I feel IX was for me.

I'm currently replaying all the FFs as we speak, so I may come back to flesh this out some more.  FFI (FF Origins on PS1) at the moment.

Game: Final Fantasy VII. The scope of the story is just so intriguing to me. I think it has the best highs of the series with a medley of sad, happy,funny and action intense moments.

Character: Definitely Yuna from FFX. She is the anti damsel in distress heroine that the series is unfortunately plagued with. She don't need no man to save her. At every point you think she does...she saves herself. She is a dedicated hero who often shoulders tye burden of the world on her shoulders. She sacrifices all of herself in effort of bringing peace to The world.

Final Fantasy VIII and Cloud Strife is my favorite character. VII is an amazing game with a better story than VIII, but purely as a game, I love VIII much more.

Balthier + Auron i thought were excellent. 

Final Fantasy VI s definitely my favorite and that's never likely to change. As for my favorite character, that's a hard question. I'd say the best casts are VI and IX, and also I like Lightning (judge me).