Yes but Carmack also said that he now prefers D3D[1] and that difference between OpenGl and D3d does not really matter: "It’s interesting how little of the technology cares what API you’re using and what generation of the technology you’re on. You’ve got a small handful of files that care about what API they’re on, and millions of lines of code that are agnostic to the platform that they’re on." [2]

[1]http://news.ycombinator.com/item?id=2313661

[2] http://www.maximumpc.com/article/features/e3_2008_the_john_c...

It isn't because OpenGL is better. It's simply inertia. Don't take my word for it - take Carmack's.

http://www.tomshardware.com/news/john-Carmack-DirectX-OpenGL...

I do all my graphics work in OpenGL, but I'm aware of its shortcomings.