There's no reason that a Wii version can't play as well or better than a PS3 or 360 version of a game. On the other hand, Wii versions will never look as good as the PS3 or 360 versions of the game (not unless 3rd parties just started lessening the quality of the graphics in their games due to the Wii's impressive sales something that I hope never happens as I love games that both play as well as they possibly can and that look as well as they possibly can).
Heavens to Murgatoids.