I think any FF after X has really good voice acting. Not that X was bad all around, it just had a lot of weirdness to it.

My favorites include Andrea Bowen's Aerith in Crisis Core, Lightning in XIII, and SERAH too cause she's voiced by my all-time favorite VA - Laura Bailey! And I really liked Vanille's voice as long as she wasn't going all "aHa, nya-ha" and all that anime bulltrout. I really liked her accent.

And any voice in XII qualifies, really. I think it's easily one of the best cast games period, probably owing to the fact that most of them were theatre actors and that the script lenses itself to the voices so well.i still can't get over Fran's voice, and Larsa is what all 12-year-old blue should sound like - actually being voiced by a boy.