Could be a bit better.

User Rating: 7.5 | The Grim Adventures of Billy & Mandy WII
As my first Wii game (along with Sonic and the Secret Rings) this game was acceptable. At first, it's awesome button mashing fun, but it does tend to get boring after a while. Story Mode is good, but SHORT. There's only about 5, 6, or 7 levels (depending on which character you pick). You can play as Billy, Mandy, Grim, Mogar, Fred Fredburger, Nergal, Nergal Jr, Eris and more.
I thought this was supposed to be a Wii game? There's only one way to move around and that's to move the Wiimote up to do a heavy attack. I mean, COME ON! The point of the Wii is to move around. All you do is move the Wiimote up.
The finishing moves are okay. Some characters have good ones, some characters have crappy ones. But Fred Fredburger's finishing move is ridiculous. He drops a giant box of Nachos on the opponent. How stupid is that?!!? Grim's is quite good. He opens up a portal which sucks in the opponent. And Nergal's is cool, too. He electrocutes the enemy with the tentacles on his back and says, "you're in for a SHOCKING good time".
The game is good, but you might want to rent it first to see if you like it.