I think you guys are basing stuff way to severely on the tier system.
It truly does depend on the player. You are never even going to come close to playing a character perfectly, so the thing doesn't apply to us at all. You can only play to the best of your ability. And if I play better than Alex (lolno), it doesn't matter if I use Fox or Mewtwo; I'll win.
Just sayin'.
But you would undoubtedly kick more BUM-BUM with Fox than Mewtwo, even if you beat me with both anyway. And that's why the tier system makes sense.
****.