i'm pretty convinced that microsoft and sony are behind this, they paid a lot of money to get exclusive games on their consoles and pc, so games can be played by anyone, all EXCEPT the wiiowners. In other words, i think they pay the developers to not release their games on the wii.
And so forth, the wii will have almost no exklusive thirdparty games next generation, it's a real smart strategy from sony and microsoft, although the effects hasnt begun to show just yet.