My pic for each system:
XBOX 360: Mass Effect
This was a hard choice, because there are so many awesome games for the 360. I know many people would hate me for not choosing Halo 3, but I would call it the best multiplayer game. Mass Effect has amazing graphics, storyline, and gameplay. If you enjoyed Star Wars Kotor, I highly recommend you get this game!
PS3: Call of Duty 4
Some people will argue that this may be better on the 360, but this is my opinion. CoD4 had to be on the list somewhere, so why not for the PS3. This is definitely one of the anticipated games that will save the PS3 from the hole it started in when it first was released.
Wii: Resident Evil: Umbrella Chronicles
I know a lot of people will say that Super Mario Galaxy or Metroid Prime 3 are better than this. The reason why I chose this game, besides the fact that I am a huge RE fan, is that it's easy to learn and fun at the same time. In my opinion, it was pretty hard learning the controls for Mario Galaxy and Metroid Prime 3, so I really liked this game for being quick to learn. If you are new to the Wii and need a good shooter, I recommend this game.
PC: Tabula Rasa
Normally, I'm not much of an MMO person, but this game inspired me to give it a try. There are hundreds of missions your character can take in this game, and the gameplay is well thoughtout and a lot of fun. However, I chose this game because of the unique character engine. Now, you can clone your character if you wanted to specialize in a different class than your first character, so you don't have to start over with a brand new one,
Nintendo DS: Legend of Zelda: Phantom Hourglass
Zelda games haev a reputation to keep up with the hits like Ocarina of Time and Twilight Princess, and this game definitely keeps it up. I was really excited for this game to come out, and when I got it I couldn't stop playing it. It's a great adventure, and the DS uses the dual screens very well.
The only reason I am not doing PSP is because I don't have one