Most games on the market today sell anywhere from 30,000-200,000 copies in the first month. SSBB went far past the norm. As I said before, this game will be as big as Halo 3... In the long run it will sell more copies (More Wii owners).
At Gamestop there were two types of games, games that sold for a few weeks and people stopped buying them, Burnout Revenge. Then there were games that sold at least once a week at a very constant rate, Mario Kart DS.