Gotcha Force (GC) - Can't say I've ever met someone who had actually heard of this game, but it an awesome fighting / beat em up game which pretty much has the plot of Transformers (series not movie), but instead of giant robots, its small toys. I know that seems a little backward, but seriously, this game is the most fun I've had with my GameCube ever. Not that it set very high standards.
Goldeneye 007 (Wii) - I'll be honest, I played the original N64 Goldeneye when it came out, and I didn't like it. Maybe I just sucked too much at it, but this one is probably the best shooter on the Wii. Once again, not exactly high standards, but it does a lot of things right. Now if only they would have put Pierce Brosnan in there...
Mirror's Edge (360, PS3) - Far from a perfect game, but the central free-running mechanics work quite well and there are a number of levels that balance a kind of puzzle platforming with the more intense action sections. It got a lot of bad rap, but I'm not entirely sure why. Give it a shot at least.
Sonic Adventure (DreamCast) - May be 3D, but I still consider it the last truly good Sonic game (though I don't consider Adventure 2 all that terrible). A fairly solid story followed by fun and pulse pounding gameplay with a constant boss that keeps evolving and changing each time you face him. Not to mention the story switches between all the major characters. Yeah I know no one wants to play Amy, but seriously, E-102 Y is the best characterized robot of all time (yes, more so than the Portal ones), with one of the most tragic stories of any video game character.