Metroid Prime 3 does some new things, some great, some not so, but overall it's a fantastic game.
The graphics are really great. Not that much has improved since the previous Prime games, but it's really one of the best looking games on the system. What makes the game look so good is the artistic design. You'll really get blown away when you reach skytown. Everything looks just amazing. All the buildings are airborne thanks to some huge jet packs, and you travel between them with the use of cannons and your trust worthy grapple beam. Every planet feels fresh and exciting thanks to inventive design and good looking graphics.
The sounds are really nice. All though it isn't orchestrated there are some nice remakes of old favorites, and the new music sets the mood just right. Sound effects are great, and especially Samus's footsteps sound awesome. There are also a lot of nice voice work this time around. It's okay, but nothing more than that. There are a bunch of standard dialog, but who cares!
What's most interesting about Metroid Prime 3 Corruption is the controls of course. You control using the wii mote to aim and the nunchuk to move around and it feels just amazing. It takes a little while getting used to, but after some hours you're fighting bosses with precision and speed. This is probably the biggest new addition in Metroid Prime 3. But also the voice acting, and slightly altered gameplay makes for a quite different Prime game than the previous two. You're not as lonely as you once where, and I kinda miss that. Samus has always been alone on her missions, and fighting alongside other bounty hunters and space marines isn't all that great. It works good, but not so well suited for a Metroid game. The game still feels a lot like Metroid Prime though, and that's good. There are a bunch of hidden suit expansions for you to collect and they're all very well worth searching for. The boss fights this time around are also very good. They're not as big though, but still very much fun. The game is more cinematic than any other Metroid game, and it makes the story more engaging. The game has pretty much the same length as the previous games and that's good enough. It's one of the very best reasons to buy a Wii, and I think almost everyone would find this game entertaining, much because of the controls, but also because it's a great game.