I should add that, because the nominal price for a Wii game is $10 lower than for a 360 or PS3 game, there's a natural implication that the money made from selling the game will be less per unit. Combined with the wider demographics of the Wii audience, its a huge risk for a publisher to put down a lot of money for a good game on the Wii. A good game... "for what demographic?" is really the main issue. You can't sell a bazillion copies of GTA4 on the Wii, because the Wii audience isn't nearly as prone to buying it, due to demographics.
Nintendo can get away with it (they spend $10s of millions on their titles -- heck, Super Maro 64 cost $30M to make, and that was in the N64 era), because not only do they make money indirectly by selling consoles (by making the console cooler via great titles), but they also make more money per unit, because they don't need to pay themselves any licensing fees per unit to publish software for their own console.
