Best game I've played is NFSMW. There's other racing games I might like, but I haven't played them. I did play the first 2 Gran Tourismo games for Playstation, but never got a PS2, so I couldn't play the rest of them.
I tried the Flight Sim trial and I had a hard time controlling the plane w/ the keyboard.
Graphically, the Crysis demo was good, don't plan on getting the full game myself as I'm not big on FPS games. COD4 looks good, never played it myself though. My brother has it.
I like AOE2. Best strategy game and it can run on a P1 system...
It's funner to play it during class over the school network when there's nothing else to do.