I've been playing Oblivion since it came out a year and a half ago. I'm on maybe my tenth character, and I don't think it will ever get old - at least not before Elder Scrolls V - whenver that is.
Bethesda Softworks also bought Fallout and will be releasing a Fallout 3 soon, I think. that looks promising.

Plus of course Half-Life 2, Episode 3, again, hopefully sometime soon. I liked the HL Episodes 1 and 2 better than HL 2 because there was more interaction with the resistance. I felt pretty alone through most of HL 2, but still it was very cool. Gotta love killing those Zombies. ;-) I've played HL2 through 3 times, and the newer Episodes each twice.

I started NeverWinter Nights 2 several months ago, but still haven't gotten very far through it. Although that's a beautiful game too, visually speaking, it's very "technical" in that you have alot to do with how your character performs based on decisions you make - a true RPG.
I bought Bioshock right after it came out and thought it was a really unique, excellent game and had a blast playing it all the way to the end - in less than 24 hours. But it was so linear and mapped out, I have no interest in playing through again anytime soon.

The sign of a really good game, IMO, is one which you win, and want to start all over again, not just stick it on the shelf.

I''ve played Crysis through several times now, but one of the best things about Crysis (Oblivion too), is the mod tools - The "Sandbox" Editor is amazing and beautiful.

And the really cool thing is, now that we have dual and quad core CPU's and mega-powerful video cards, and the technology is continuing forward as the prices drop, the games of  even the near future are going to be even more amazing. Let's just hope the ideas and storylines continue to develop along with the graphics.