DirectX is the industry leading multimedia API, and sets the standards for graphics quality/performance (opengl was once ok but has been trailing for many years now(theres a reason next to no commercial games use it)).
some game developers yet uses OpenGL
for ex ID software games are all OPENGL,ie quake 2, quake 3, quake 4,doom 3, wolfstein,Rage etc
Doom 4 is not out yet but will be using OpenGL ID engine 5
