OpenGL is already a competitor of the video part of DirectX, and a good one (to the extent that in some cases the same game on the same hardware could get better performance in Linux than it did in Windows). But thanks to some Microsoft fudging of OpenGL in Windows years ago (and probably a lot of back scratching), many game devs decided to go exclusively with DirectX. I suppose it might be possible to clone DirectX, so Linux ports could be more easily made, but I assume that it would bring up a whole pile of legal issues...might be better just to stick with improving Wine.

In any case, it still comes down to the big game developers and publishers. As long as they are unwilling to bother with Linux, there will be very little gaming. What little is currently available isn't too bad, by the way, although a lot of it is lacking polish....there are several games that work beautifully, but have very little or poorly crafted content.

it's cause windows is closed source
so you need actual windows files.

This has been the main reason linux has never caught on for desktop use. Even secretaries addicted to minesweeper can't dig the linux versions.

there just isn't enough sales to dedicate the resource fork for games into linux.

It's a server OS designed for serving files and math computing