Comparing sales data for for videogame consoles upon release is kinda useless nowadays seeing how the demand for the machines far surpass the supply available. In the UK, MOST of the machines available at launch went to fufil preorders, with only a handful available to high street stores. I've seen a lot of unhappy people walk into stores trying to buy one and have just been turned away. Although there will be more shipments of the console... possibly this week and up till xmas, most retailers in my area don't expect any machines till after xmas. Thus first week sales are really not a good reflection of the success of a machine at launch.
Aside from the lack of units available the Wii seems to have had a good launch over here, there's a lot of buzz and attention from the media about it at the moment, far more so than the GC or Xbox 360 ever received.
=)