I love Fran and Balthier's voices, and Penelo's is pretty rad too (I heard Tara Strong was doing it, but I guess this was just a rumor). Larsa's actor fits him very well, too.

I don't have a problem with anyone else's voice, they all fit, Vaan's included.

My favourite voices would probably be Fran's, Larsa's, and Judge Drace's.