Windows 7 is undoubtedly the king of gaming right now. In another year or two, I'm not so sure the scale will be so unevenly balanced. Steam is one of the most powerful gaming sources for computers, and they've taken a severe disliking to Windows 8 and where Microsoft is heading. It's pretty obvious that Steam's interest in Linux is here for the long haul. It only further solidified their stance after they were able to successfully port several games to Ubuntu and with a minimal amount of development have them running as good or better in Ubuntu as they run in Windows 7. Different Linux distros have also been benchmarked to test their gaming capabilities, all of which did remarkably better than I expected. That being said, predicting the future of technology is pretty useless because things change so drastically on a regular basis. If you want a gaming rig set up and running tomorrow, I'd get Windows 7 for that. But like I said, months/years from now it might be a different story.