Brutal Legend is the most awesome game that I've ever not wanted to play.
It's weird... I love the style, humor, and writing of the game, and the world is a great idea, especially since I'm a metal fan. The soundtrack is great, and just driving around killing stuff with metal blaring out of the vehicle's radio is pretty nice.
But the meat of the game, the gameplay, is merely 'ok'. To the point that when I stop playing it, I don't really feel compelled to ever start again.