Well "best" is subjective but if I had to give my opinion I'd say Final Fantasy X probably had the most interesting story.
Only to be hurt by a pansy lead. I hate Tidus. I do agree it hit a good mark on the story.
Hmm....For the life of me, I can never remember 8's story.
It's the one with the time travel and the memory manipulation and they were all in an orphanage together but they dont remember and they have a flying school and then they are in space to free a witch to stop the monsters falling from the moon and OMG-MAKE-IT-STOP