The best for me is FF7. I have played the PRE (not post
) PS games and I must say, they are damn good too.
But 7 is tatooed on my heart. An epic. Chocobo Breeding, Gold Saucer, The Huge Storyline, Characters that you actually cared about, THE BEST BAD GUY, Fantastic Music (I think the best of any) and just overall sweetness.
Also, its the only one I have gone back to.