Like, ever, or just recently?
TIE Fighter was one of the greatest games I ever played. I still have my MS-DOS floppy disk based version. Runs just great in DOSBox.
Mechwarrior II and III rocked super hardcore as well.
Sam and Max Hit The Road was hilarious. Still makes me laugh 15 years later.
Starcraft I is still pretty much gold standard stuff, even decades later, and with its sequel making everyone forget the original.
Max Payne 1 and 2 made bullet-time super cool on PC, even as the Wachowski brothers were screwing up their property by releasing Matrix:Reloaded and Matrix:Revolutions.
Half-Life 2 is still one of the only games I can think of where the physics model was well incorporated into the gameplay. Oh, and it didn't require any PhysX b.s., either.
More recently, I've liked Modern Warfare 2, Splinter Cell Conviction, Batman: Arkham Asylum, and Civilization 4.
Some games I haven't liked recently: Crysis, Left for Dead 2, Galactic Civilizations, Need for Speed: Shift. I won't go into why I feel the way I do, but that's not to say that you might not enjoy them.
I'm currently playing Bad Company 2, and thus far, don't like it much, unfortunately. I was initially drawn to the game because of the completely destructible environments, and the concept is vastly underused in singleplayer. The storyline is horrible (even worse than The Rock/24-lite stuff in MW2), your squadmates have all the intelligence of pond amoebae, and the missions are all pretty much rip-offs of other, better FPS. The only time I smiled was when they inserted that inside joke about SPECOPS losers running around with heartbeat monitors - a direct zing at MW2 - but other than that, meh.