yea, I'm not gonna list fifty...how about 5, but with reasons for them?
(in no particular order, and yes, this list changes constantly, as it should)
Red Dead Redemption- The best sand box game I've ever played, with a great story and great characters. People may say it's just GTA4 with horses, but atleast in RDR the camera doesn't keep zooming on the horse's ass, AND there's no Roman.
Mass Effect 2- Best characters in a game I've ever seen, by far, and all the problems I had with the first (poorly done inventory system and the Mako) are removed. Also possibly my all time favorite final mission in a game, ever.
Halo 3- Yea, that's right, Halo. I've played this game more than any other, and I've enjoyed every second of it. And screw what people say, I enjoyed the story. The multiplayer and co-op don't hurt, either.
Dawn of War: Dark Crusade- I'm not really a big fan of RTS, because I suck at them, but for some reason I'm actually good at this one. I just love the over-the-top nature of the 40K universe, and how this game does a really good job of portraying it.
Star Wars: Knights of the Old Republic- I really don't think this one needs any explanation. Greatest Star Wars game and one of the greatest RPGs ever made.