FFVI - My personal favorite, great story, great villains, great style, great music and great characters (specially Shadow)... one of my favorite games of all time.
FFVII - After playing FFVI, I thought this one was a step... back. Music just sux, why MIDI? Also, characters are way too plain and clichéd... wtf with Mr. T? And the just plain crazy for almost no-reason called Sephiroth? Just a plain game for me.
I would like to play VIII and IX tho, they seem really cool, specially VIII.