Based on the fact that Server Operating Systems are more stable.
So, I guess Server Operating Systems is a good choice for gamer,
am I wrong?
sounds like a silly question.
Do you mean Windows server editions? Although Linux can run games with Wine and Steam is creating a Linux client, I doubt that would be a good choice at the moment for the best games experience.
While you can use those as a desktop (or at least in the past), I would assume that most games are made for the regular Windows desktop versions, not the server ones. So in that regard, go for a normal operating system.
Operating systems made for servers are (or should be) more stable than the desktop versions. But that's for services (websites, databases, ...) that should run 24/7 - not games.