WiiFit was sheer Nintendo genius, has already made them a bucket of money and will undoubtably make them even more.
The brilliance of Nintendo here is that they continue to innovate, to the best of my knowledge the concept behind WiiFit could easily have been attempted on the 360 / PS3 but they just dont have that Nintendo genius to risk it and, more importantly, pull it off.
I think Mario Kart is going to sell a lot but, as a lot of people have already mentioned, WiiFit will be the system seller.
I cant see Rock Band selling that many copies on the Wii as it is very expensive compared to the cost of the console. The killer thing with WiiFit is that it appeals massively to the female audience, I have never known soo many of my female friends into a console in the same way that they are into the Wii.
