I think that sports titles in general just sell less because the genre is mature and there are not compelling new features from year to year.
As for the Wii, well why would you focus resources on a platform that is graphically and processing inferior. They probably list the features they want to build then decide whether or not it is feasible to do them 100% on the Wii. Instead they should spend more time making the motion controls better on the Wii and I think they have done that with Tiger Woods.







