Earlier i thought FF VII was the best but i think that was cause it didnt really have any competition at that time.
But i replayed it for a short while ago and it wasn't really as good as i thought it was, the story and characters and everything with it felt old and that wasn't simply because of the graphic.
Now i would say that FFX is the best since it was the first and almost only game that has touched me emotionally, i almost cried in the end