I was a big fan of the first Mass Effect game from Bioware. It had some issues; texture pop-in, slowdown, and some random glitches, but it was a great game. The developers had always talked about Mass Effect being a trilogy so I knew that I'd be able to look forward to what they'd improve in the sequels. And, having seen some of the trailers and gameplay footage for ME2, I can't wait to play this game! Everything from the interface to the story and dialogue just seems ten times tighter and more refined than in the first game. Here's a video showing off the "Adept" class that you can choose from. The Adepts are basically magic users in the world of Mass Effect:
I didn't acctually play as an Adept in the first game. I played as a combination of an Adept and a Soldier, called a Sentinel; but just the way that they've made the powers look more impressive and significant is making me wish I had.
Here's a trailer for one of the party members you can get, Subject Zero, she's definately darker and has a filthier mouth than any of your party members from the first game. However, her attitude fits because they've always talked about this one being the "Dark Second Chapter" in the trilogy.
Long story short, I can't wait for January!