Super Smash Bros. Brawl
So at my friend Paul's behest I got the kids Super Smash Bros. Brawl for the Wii sooner rather than later -- he told me how much fun his own boys had had with it since they got it around Easter. It's pretty much all they've been playing since.
One thing I think is interesting, though -- rather than playing with the Wii Remote, they opt for the GameCube controllers. They're much more comfortable with them than the Wii Remote. Now I read that Nintendo is readying a new controller in Japan for the Wii that's essentially the GameCube controller in white plastic, to match the Wii. Guess my kids aren't the only ones.