I'm not a hard core gamer at all, but I finally took the XBox 360 plunge a few months back pretty much specifically to play Red Dead Redemption.
However the game that I burned through pretty much over the course of a single weekend was Alan Wake, which I found immensely impressive from a story-telling perspective. It's also a game I had never heard of and I only had access to because it was bundled with my system. Totally worthwhile.
Of course now I have no games to play and will probably just hang tight until LA Noire comes out.