Well, yes, there's a bit of a self-selection problem evident in that only the people with computers sufficiently powerful to run Steam games will use Steam. But pretty much any computer around these days can use Steam. This is certainly a sample space problem, but it's minor enough.
I would disagree that it is minor enough.
You're asking gamers what their computer specs are, and assuming it is an accurate enough random sample of all computer games?
Call me skeptical.