Manhunt 2 is not the worst action game out there, but there are also a lot better titles to choose from.
Story is not clear even after a few hours of gameplay, which is all the more reason to push you away to play something good on your Wii like Super Mario Galaxy or Metroid Prime 3 for example. Although Manhunt has "2" in it, it has nothing in common when compared to the original game. You play as a scientist named Daniel Lamb, who has gotten himself in a mental institution and when a riot starts he escapes with a friend along. Manhunt is now on, because the Project (whatever that is) wants them both dead. It's now up to Daniel to hide in the shadows and find out what's really going on.
Graphics are horrible: everything is muddy and blurry. Wii can do much better than what Manhunt 2 has to offer. It doesn't help much either that the game uses colors quite economically: everything is mostly grey. Sound design on the other hand is great. Voice acting is solid and all the sound effects are appropriate and effective.
Controls are stiff, but functional. Problem is that the different executions are made by the Wii remote and you don't have enough time to see what you are supposed to be doing. This makes most executions to just fail utterly. Also because of the censorship you don't see much of the executions anyway so this takes most of the shock effect away right from the start.
Game is completely linear and you need to play it just the way the game wants you to play it. You can't do any experimentation. When this is combined to the fact that the game uses checkpoints it's pretty clear what happens. You need to play those same sections again and again until you figure out what you are supposed to be doing in order to proceed.
Manhunt 2 is not a bad game, but it doesn't do anything that other games hadn't already been doing a lot better on the Wii. The game trusted too much on its own shock value and now the time has done its job: Manhunt 2 is not worth your time and money anymore.