Actually DirectX is lots of fun with a really great API, good documentation and some totally awesome tools. Also DirectX 11 already has some great features (I think there is something like texture arrays as well?) and I have no doubt that DirectX 12 will improve on it even further.
The biggest advantage of OpenGL is that it works on so many different platforms and maybe its extension system, which on the other hand results on many different rendering parts for different hardware if you want to take advantage of the latest features or just get the best performance on all kind of hardware and that gets very ugly very fast.
and the winner is going to be a laughing 3rd one called OpenGL grin
but OpenGL would need a huge marketing boost, maybe as large as DX has by Microsoft, because its technology is not worse at all, frequently more advanced.
With Valve pushing Linux and NVIDIA pushing the bindless extensions, OpenGL is currently getting lots of attention. Also with the mobile market mostly based on OpenGL ES, there seem to be more people interested in using OpenGL than ever.
Did you see those presentations claiming a 5x to 15x performance improvements if you are CPU bound by the graphics driver? There now finally is a reference GLSL compiler and Valve is working on an open source OpenGL debugger for linux.
