1. Super Smash Bros. Brawl
There was never really any question as to what game would be number one. The most hyped game to ever be released for the Wii delivered on all fronts (well, nixing online). Brawl took the already successful Smash Bros. series and added more characters, more stages, more items, more modes, and more moves. It played just as well as previous ones but new moves and items meant new strategies.
It looked better, offered a deeper single player mode, but kept all the classic modes as well. The Final Smash was the ultimate item pickup to add into the craziness. This was exactly the kind of expansion to the series the fans wanted.
Despite all this, the game somehow became more accessible. I have played hours of this game with my young niece and nephew. And I have played hours against my hardcore brother who knows every special move for every character. It remains fun either way. Like previous Smash Bros. games Brawl will still be being played years after its release.