wii sports was a revolutionary game though, this is just taking it to the next level. You can't have expectations that WSR is gonna sell as much as wii sports, that's would be like expecting a sequel to mario 64 to sell as much as mario 64, or mario 2 on NES to outsell mario 1, or tetris 2 to outsell tetris 1. Of course it's still gonna sell really well, but it won't sell 5 million, perhaps about half that.
currently playing: Skyward Sword, Mario Sunshine, Xenoblade Chronicles X