In forums you frequently see flame wars over OpenGL vs. DirectX. The language or API in question is irrelevant. These threads are typically started by n00bs trying to decide which one to learn.
Microsoft was a founding member of the OpenGL architecture review board. In February of 2003 Microsoft announced its departure from the standards body. Microsoft stated it would "focus our energies on improving and evolving our own Windows graphics platform." OpenGL and Direct3D, part of the DirectX API, are very similar, both serving the purpose of a uniform API for applications to render 3D graphics on any supported graphics chipset. Microsoft has chosen to abandon the standard, which presumably means no assistance in supporting the standard's use on the Windows operating system. Software developers will be more inclined than they already are to use Direct3D as opposed to OpenGL when developing for the Windows platform. Whether or not Direct3D is technically superior, there are advantages to standards, especially for the users (customers) and non-Microsoft developers. Choosing OpenGL a developer can target multiple operating systems simultaneously, giving more choice to the developer and user. Open standards also free developers and hardware manufacturers from licensing fees and restrictions.