iOS - OpenGL ES
Android - OpenGL ES
Mac - OpenGL
Linux - OpenGL
HTML5 - WebGL (based on OpenGL ES) - even in IE!
Emerging platforms like Tizen, Firefox OS - OpenGL ES/WebGL
DirectX is just for Windows and Windows Phone. Isn't it getting to the point where the bother of having to write a DirectX port might cause developers to skip the Windows platforms, or stick to OpenGL on Windows desktop? Windows isn't as overwhelmingly important as it used to be, and couldn't the fact that DirectX is different start to work against MS? Imagine if Blackberry came out with their own custom 3D API - wouldn't that only serve to hurt them?