My humble answer would be Windows 7 Pro/Home 64bit. Unless you have or is buying a touchscreen, then Windows 8 for longterm benefits.
The whole start menu thing missing, for me personally, is kinda void, when one knows about the secret menu (Win+X) to Shutdown Windows 8(.1) and the (awesome) Launcher still works on the Metro screen(2 times Win-key(iirc) from anywhere to start any program fast). I thought the best feature of Vista/7 was and is that Launcher, I use it so much I should pay taxes but I never ever wade through the Start menu itself, unless I wanna find the "Startup" folder, which for some reason I didnt shortcut.
I dare to say that Launcher is the single most productive quantum leap in Windows since Alt+Tab or so.
So the short answer 7 unless you got a touchscreen, since you said (dedicated assumed) gaming rig. If you don't find fidling with stuff and adjusting stuff and get surprising features and hickups any annoying to your gaming, go 8 for longterm gains.