Opengl

Riddle me this:

If OpenGL is supposed to be just as good if not even better than Direct3D (Not talking about DirectX here), then why don't developers use OpenGL to program their games generating some extra sales on GNU/Linux and Macintosh?

You wanna know why? OpenGL sucks.  There was a time when OpenGL was good; most actually preferred to write using OpenGL than Direct3D.  Then Microsoft said "No.", and ever since then Direct3D has been infinitely better than OpenGL.