Comment Re:DirectX is obsolete (Score 1) 135
If you write a game that uses Direct3D, you can easily target Windows, XBox, and Windows Phone. If you write a game that uses OpenGL, then you can easily target all of the major desktop, mobile, and console platforms. If your game runs on a generation-old console, then it will run on current-generation mobiles as well. This gives you three markets: First release for high-end PCs, second for consoles, third for mobiles. You can get a solid revenue stream out of each one. You don't lose the Windows marked by choosing OpenGL, but you do lose every other market by using Direct3D.
That said, the APIs are so similar these days that you'll typically use some middleware to provide the abstraction. All of the important code is written in the shaders and these are much easier to port between GLSL and HLSL than they are to port between different GPUs and maintain performance.