What operating system should I get?

I'm planning on getting a new computer, I have everything worked out but what operating system I want.

I refuse to buy any Apple operating system for the lack of optimization and user control. There are other operating systems I like a lot (Like Linux) but they aren't as compatible with things I like to do on my computer.

The only operating systems I have ever found use out of are the Windows operating systems. I was going to get a Windows 8 computer but after hearing really bad things about it and trying it out for myself, I've decided I want to avoid it like the plague. But, at the same time, I also don't like Windows 7. I still have constant maintenance problems with it today, and the interface tends to make no sense sometimes. It's extremely annoying to deal with.

So, I started reminiscing about the older Windows operating systems and how easy and simple they were compared to the new ones. The I began to wonder if I should just get a new computer then install an old version of windows on it. I mean, why not? What exactly are the differences between the current version of Windows and the older one's, other than visual and layout changes? If you would recommend it, which version should I get? WindowsXP, Windows 98, Windows 2000, what?

Or, should I get a different operating system, that perhaps I haven't heard of or considered?

I do a decent amount of gaming and modding, I like Team Fortress 2, Dota 2, Bioshock, Half Life 2, Portal, Minecraft Etc. I also listen to a substantial amount of music, I use Foobar2000 for that. I absolutely do not use any social media websites (Unless you count email, Steam, and YouTube.). Also, I use my CPU for school a lot so I need access to good document editors, and Firefox. Other than that I don't have any use for other features and I don't care about how user friendly the operating system is as long as it is efficient.

Also, don't tell me to design my own operating system. I don't have the patience or time to learn to do that.