If you really need another example of this happening why don't we look at the DS. It spent 2 years of it's life selling on nothing but Nintendo games and the (very rare) good 3rd party game. However, 3 years later comparing the 3rd party support of the DS to the PSP is like comparing the PS2 to the GC. The PSP gets the occasional third party game but the vast majority of support and big games goes to the DS.
I'm not really sure why anyone would expect the Wii to be any different. They both launched with similar developer perceptions and both are outselling their competition in a similar ratio. Except the Wii is doing a much better job of outselling the PS3 and 360 than the DS did for the first year (in which the PSP actually outsold it some 15 weeks or so). Obviously looking at developer actions and statements this shift is happening much faster on the Wii than it did on the DS.
I don't think the PS3 and 360 will be lacking in good games this generation. Heck, the GC wasn't lacking in good games. That's pretty obvious considering it has the best attach rate of any game system of all time. It just doesn't make much sense to expect the 360 and PS3 to have the majority of future 3rd party support in the future.
