ahhh dammit FF VI is my highest easily, great characters, great graphics (much better than FF7, good 2D > bad 3D), amazing music (best of the series), and my favorite villain of all time. Not to mention the game starts out linear and ends up totally unlinear, theres just so much to do in the second half of the game.
...followed by either 4 or 7 (7 is more complex and a better game overall, but 4 just had that great Final Fantasy feel, whereas FF7 doesnt feel like an FF at all)