It would seem that people are really starting to see value in the XBox 360, and this is something Nintendo shouldn't take lying down. If they really hope to continue with the Wii for 2+ more years, then they need to make it a hot-ticket item once again. They can do this by either lowering the price, or offering bundles that include more than just Wii Sports/Resort. Start by adding a second Wii Remote Plus and Nunchuk to the basic $200 package, and then it becomes far more complete since you can play all of the Wii Sports games with two people. Then, offer software bundles that include another game, such as New Super Mario Brothers Wii, Wii Fit, Donkey Kong Country, etc. They could also make special colours for these bundles to make them more attractive, like red for Mario, green for Donkey Kong, etc.
As for game sales, XBox 360 games and PS3 titles are always front-loaded, so you have to look at total sales for the big picture. Did you know that not one PS3 game has sold over 5 million copies? Meanwhile, the entire Wii top ten have all sold over 7 million.