A large portion of the Windows XP user base is composed of people who are using it to play games, mostly because they have older hardware. Windows 7 may look prettier than Windows XP, but it also comes with higher system requirements.
Now, if a user started thinking about Linux as a possible alternative, no matter the distribution he chooses, would he be attracted by the gaming on the Linux platform? Most likely not. It would be easier to speak from a general point of view, but I think that a more personal example is at hand. Besides my Linux distros at work and at home, I also use Windows 8.1 as an alternative.