Wii owners...buying Nintendo games. Who'da thunk?
Well when most of the best games on the system are made by Nintendo, that's why. It's the same reason why Nintendo games sold the best on the N64 and Gamecube as well as the DS.
The only time a third party released a major quality title with
mass market appeal on a Nintendo console that rivaled Nintendo's best in the last 10 years was Capcom with Resident Evil 4 and guess what, it was the best selling Gamecube game in 2005. Not to mention the port of it for the Wii has sold around 1.4 million copies which is the same as the 360 version of Dead Rising and just 100,000 less then Lost Planet.
The funny thing is though both Dead Rising and Lost Planet got huge advertising campaigns while Resident Evil 4 Wii didn't. And yet, just as many people bought RE4 Wii on the Wii, as 360 owner bought DR and LP.
If more third party released games of RE4's quality and they'd bother to market them, they'd be rewarded with sales just as good, if not better.