Isn't the real reason because there's really nothing else on the Wii that can appeal to everyone?
I just got a Wii, and I bought my first few games at a buy 2 get 1 free deal. To me it felt that NSMBWii was a given, and I also got DeadSpace, but it took me forever to get a third game.
There were a lot of games, tons of genres, and a lot of it seemed good but nothing really stood out. NSMW stands out as a game to get (apart from being Red).







