i don't know why this happens
the game is selling very good, the sales are increasing fast, it has legs, good reviews and already a million seller!
it's not the type of game that will sell only at launch
also, you can't expect 5 million that easily with a userbase of 17 million, but with LBP it is possible and it can happen!
about Wii Music, think it will have very high sales, it will pass 5 million for sure and keep going.....
don't mind my username, that was more than 10 years ago, I'm a different person now, amazing how people change ^_^