If there is a problem, it is likely a driver issue that will likely get resolved eventually when a new driver is released. Games run more or less perfectly fine on 8, just like 7 (there is occasionally an incompatibility hiccup here or there but those often get fixed eventually). If you are worried, then google if your games run fine on 8.
Unless there is something that is exclusive to 7 or older OS, then just get 8