Linux is indeed better. Not because of Open Source (the code doesn't care) but because it has fewer bugs (about 0.1% of the bugs per kloc), non-intrusive strong security (rated EAL 5+ on conformant hardware, conforms to B2 Orange Book standards), superior multi-processor support, superior memory management and superior networking.
Graphics? Not an OS issue. That's a GUI issue. Never confuse how something gets data with what it then does with it. The GUI is not central to Windows (as demonstrated by console mode startup, but should be obvious to anyone running it as a headless server). The core OS functions are, and always have been, resource management, virtualization, security and stability. (Filesystems are virtual layers on top of physical disks, so are resource management and virtualization.)
Linux is better at the things an OS is meant to do. Windows has an adequate GUI, but the OS is abysmal. Besides sales, the only reason the game industry likes Windows is that it has useful libraries - DirectX (an alternative to the functions the GUI itself provides) and easy access to GPU functions (bypassing the OS altogether, running on bare metal).
The reason Linux doesn't have these? Look in the mirror. The face you see was quite capable of working on GGI, KGI or Linux Framebuffers, of helping in the Berlin project, of submitting patches for SDL or Avagadro, or even hacking Wine to improve support for DirectX, CUDA or other graphical features.
I'm no innocent myself, but I own up to my guilt, I don't blame the OS (which IS innocent).