Close between VII and X for me.
VII had a really good story, and great characters, possibly the best characters in any FF game (personal opinion there but hey).
It also had brilliantly balanced gameplay, the sub games were awesome - I must have spent as much time in the arcade and the Chocobo racing as I did on the game!
The materia system was excellent (and FFX's system harks back to that in many ways) and the summons were awesome - getting the Knights of teh Round summon still ranks as one of the best 'moments' for me in an FF game.
FFX is obviously staggering on the graphics front, but Square always push their platforms to the limit. (To be honest i expect nothing less from them now!)
It's gameplay for me went back to what made VII so special. Tweaking, tweaking and more tweaking, it felt like 'your' choice.
The story was slightly weak for me with a few of the characters too one dimensional, and the lack of real humour was a dissapointment. Comedy characters were always a strong point of some of the other games.
The setting though was the best yet, the eastern influence was a treat, Squares games more and more bind the best of western and eastern gaming into one tidy package.
And as if the longevity needed tweaking, FFX is the best yet when it comes to extra challenges if 'just' finishing the game isn't enough for you.
Blitzball was a good addition too.
FFVIII was too slow for my liking, although having a 'less then clean cut' hero was a welcome change.
FFIX locked too many locations and while 'good' felt a touch linear for my liking.
Both VIII and IX also had that annoying card game! (well, it annoyed me, frustrating yet annoying addictive!)
