I'm not saying the Wii is tanking right now, or will in the near future, but it's starting to level off and really level off in Japan. Most of the people who are buying Wii Sports Resort are probably already existng Wii owners, and I doubt that game alone has resulted in a bunch of people going to buy a Wii solely for that game. Of course the 360 has a deeper game lineup and costs less, it's got a year head start on the PS3 and has sold more as a result.
All I'm saying about the Wii is that people are getting sick and tired of waiting around for good games to come out for it. I know several people who have turfed it, or don't even touch the thing anymore.