...Just thought I'd drop a note on MP3. This game is up to par with what I expeceted and IMO it's a very solid game with it's own style that works well the Wii. I'm a big fan of FPS games like Half Life 2 and Bio Shock. If you're a fan of those games, than I'd have to say MP3 will suit you well. I've heard people say that you would appreciate MP3 more if you played all the other Metroids. This may be true, but nothing will keep you from enjoying the storyline/gameplay.
The puzzle/map aspect of the game makes it more involved, but also increases the level of awareness in the gameplay. Not to mention all the inventory and scanning equipment Samus has available on her suit. It adds a nice twist that many or all FPS that I have played don't have. For example, you can scan unknown creatures which will give you plenty of in-depth information that adds to creativity of the game. The puzzle aspect can make the game very difficult. I would reccoment turning to an online walk through i need be. A game that is difficult, in my mind, is a game worth playing and finishing. Nintendo is great at creating the puzzle aspect of a game, and MP3 doesn't fall short.
My only gripe with the game are the save points. It would of made it less frustrating if you could save it where you wanted, but I guess that adds to the difficulty of the game. Just don't start your game back up if you have to go somewhere in 45mins to an hour.
PS Read the instruction booklet while or before playing.