I have played quite a few computer games. The computer I'm on right now is a dual screen custom built computer just for gaming. And yes, I did build it. But all of my games were FPS games and when I played, the kids could not be in the room lol. Things like Crysis, Fear, COD and Ghost Recon. There are others, just not as intense as those. I also have some sim games for airplanes that are pretty fun once in a while.
I don't have any of them loaded on the computer anymore though. The ole girl is getting old and tired. She is still running the Q6600 CPU with only 2.14ghz speed. I can OC the chip to 3.14ghz and never get above 50c, I think she just doesn't have it in her anymore. I have had this chip up over 4ghz before, but it needed to be put under water for that kind of speed.
For memory, I'm running 8GB on an x64 system. My GPU is the old 9800GTX that I can and have OC'd before. This computer used to be able to run it all. But, it's time to upgrade to an i7 setup with 16gb of memory for all the stuff that I'm doing now.