What operating system do you recommend for gameserver?

I wanted to know which operating system is better for game servers than it took time and not even which operating system is better or what resources I have to be able to run a game server,
for example I make garrysmod csgo 1.6 unturned minecraft servers etc.
I don't even know which one could be better

Versions of linux are generally the go-to. There are plenty of versions of linux, each with pros and cons. However the lighter it is, the more resources you have for the game itself. Windows uses plenty of memory for itself. However you might want to check if the dedicated server supports Linux.

Unturned Dedicated Server has an in-steam tool but for Garry's Mod, I suggest checking the wiki. I believe CS also uses a similar method, using SteamCMD

Linux is the most recommended operating system for gameservers. Windows uses lots of resources.
Search for a linux which needs low requirements for the system, the better optimisation, the better gameservers fps and ping

Honestly depends on what game your running and what there serversoftware suppports some server software is windows only.