I do think FFVI is the best because it brought more nostalgia to me. It's music is a masterpeice for a SNES, that's for sure. It's characters all came to life for me, like Cyan's life, Terra's life, all of their lives came a reality to me. They were both sad, joyful, happy ended.
I also think this game has the best ending, with everything ending like a game should, insted of just flying off to some random place after a meteor almost hit.
Also the graphics were amazing, right next to Chrono Trigger, if not better.

Oh, and Kefka is the best villain in FF, Period.

(FFVI fangirl talking. But I'm also a FFIX fangirl.)