So I played a bit of the game today, the whole first ship level and a bit onto the planet. The game is A LOT different from previous Metroid games, it seems to maintain all of the basics, but there is a lot more involved now than before. I much prefer the gameplay of this one to the first Prime simply because Samus is capable of much more, and it is much easier to do it. It's a lot less frustrating, much more freedom. Due to the control scheme, the gameplay is certainly a lot quicker and more intense.
So far I have found this game to be darker than the original Prime. I really enjoyed the beautiful settings getting into the original Prime. This one is quite different, there are a lot of people around, the first level reminded me of the initial locations of Xenosaga episode 1. In fact, it was very similar, you start off on a ship, and then once you have acomplished a few tasks, aliens invade, only you play the role of the KOS-MOS type player. Of course though, movement and such is much quicker than Xenosaga. The pacing in Corruption is about perfect, a lot better than Zelda Twilight Princess.
The setting so far feels like a triple cross between Metroid, Starwars, and Xenosaga. It's a Metroid game with a lot of other characters involved (at least so far), lots of dialogue, and it seems to be story driven as opposed to purely free roaming and just doing things like in the previous Prime games; though this may change later on.
Is it the best game on the system? It probably is, but it is difficult to compare this one to Resident Evil 4. Like RE4 Wii though, the control feels much better than last generation's titles. It feels much less time consuming and much more natural-feeling than the previous titles.
Lastly, on the non-multiplayer aspect, it would make about as much sence to have multiplayer in this game as it would Zelda:Twilight Princess. It is not the same sort of game as Hunters, Bond, or Halo.
-Insert Inspiring Quote-