It's not selling as fast as the DS primarily because the DS has had 3 yrs to gather developer support, consumer interest, price advantages, and ramped up production.
Wii hasn't had any price drops, colors, or modified bundles.
Wii is still out of stock in many areas going into the holidays so the production hasn't been adequate for demand yet.
Developers still think its too early to jump on Wii's ship.
Wii is in a similar position that the DS was a year into its lifespan after Nintendogs took off. Sure they are on slightly different tracks, Wii is selling a lot better than the DS at this point in its lifespan, but to compare the Wii at a year into its life to the DS at 3 yrs into its life and declare the Wii not as successful is completely absurd.
