What a great game. If you have a wii and want a good action game, you might want to look into this great cube title.
I'll start with the single player. The graphics look good and the game is fast paced enough so that you won't notice any faults (if there are any). The gameplay is fast and fun and the third person control system works beautifully (it uses an automatic targeting system and a red dot that can be fine-tuned for head-shots or moving targets. The vehicle levels are fun and the difficulty level is right on the mark: some hardcore gamers might find it a tad easy, and causual gamers might think that it's on the hard side, but I think that's just right. It boasts 20 levels, all of a decent length.
There is a great co-op campaign that I am unsure of the length. I believe that it is more fun than the single player, though others may disagree. There is also a pvp arena mode that is not fun when you start the game but by progressing through the co-op campaign becomes more and more varied and interesting (not to mention fun).