I was about to say there's no question but I forgot about Super Mario Galaxy.
Smash Bros Brawl will probably be one of the best games of this generation, though. Melee certainly outlives Sunshine for obvious reasons.
I'm buying Big Brain Academy tomorrow from Circuit City. They say its guaranteed to be in stock by 2pm or you get a 20 dollar gift card. Plus it's only 40 bucks there. If Best Buy does price matching I can use a 5 dollar card I got for buying two movies there and get it for 35...otherwise it's WiiPlay for 45