Some of you guys are really setting yourselves up for disappointment with these exceedingly optimistic predictions. I really doubt that this game will outsell Halo's opening week, just because there's nowhere near as much hype surrounding Smash Brothers. Oh, there's plenty of INTERNET hype surrounding Smash Brothers, but that's not the same thing. If we've learned anything this generation, it should be that the opinions of the enthusiastic core gamers don't necessarily reflect that of the mass market.
Remember, the pattern for Wii games has been solid (but not spectacular) initial sales, then steady legs for many weeks afterwards. While Smash Brothers will have a good chance to win lifetime sales against Halo, expecting it to beat Halo's enormously frontloaded sales is just setting yourself up for disappointment. I think it's going to have a great debut in America, over 1m the first week - but that's not the same as Halo, not even close.