No doubt Wii Sports has a huge amount to do with the Wii's broad appeal. It's still the best pick-up-and-play game on the system, with surprising depth if you keep at it, and I have no doubt MANY people bought the Wii initially to play Wii Sports. It demonstrates exactly why motion control is exciting and doesn't seem intimidating, weird or too "gamer culture"-oriented for the heretofore non-gamer. I think one of Nintendo's biggest challenges ahead is coming up with followups to Wii Sports; most of the established franchises don't really resonate with the public the way the simple appeal of this one game does. It really is the killer app for the Wii.