Is it just / ?
I kid. But really, besides “its all a file”, if you take away the gui, is the only difference the syntax ? How libraries interact? How disks are mounted ?
If we stripped all ms’s junk out and made windows open source, would we still prefer linux?
When you get to a very basic level, is one of them more efficiently coded?
Note: Gaming performance is purely based on money spent. There’s no fundamental reason windows would have better gaming performance, it’s just that there is more money being paid to engineers and vendors to support DirectX and related tooling.
Then there’s the self-fulfilling aspect that, windows has the largest marketshare, so devs are going to spend the most money targeting it, so that they can get the most money in return, which means more people will use it, which leads to the high marketshare.
The ONLY reason Linux use is seeing the few percent blip in gaming is because Valve has dumped truckloads of cash into making it viable.
PlayStation proves gaming is just fine on Unix.