People keep saying this and I just don't get it. I've never worked in the games industry, but I have worked in the film, music, and print publishing industries and I just can't believe games would be that different. In those other industries, money talks and everything else can go fuck itself.
The people who make decisions about what comes out are not the creative people, but the money people. They decide what gets greenlighted and what doesn't, and if they saw how insanely popular the Wii was in all major global markets they wouldn't give a flying shit about what the people who worked for them wanted to make, they would tell them to make a workable franchise on the Wii or start looking for new jobs.
I just don't understand how there can be this many autonomous developers who can chose their projects at will. They would have to either a) be bankable enough to basically guarantee that their projects will turn a profit, or b) be financially secure enough to self-publish. I think the number of development houses that fall into either of those categories can probably be counted on two hands, with a couple of fingers left over. Otherwise, they do what the executives at EA, Ubisoft, Activision, etc. tell them, simple as that.
Again, I'm not very familiar with how the games industry works, but it would have to be quite different from the other entertainment industries for the Wii to be snubbed simply because the creative people aren't into it, despite the gobs of money waiting for the publisher that is able to crack the massive, and massively growing, Wii audience.