DirectX11 vs. OpenGL

I think it probably comes down to market share ... and not technical superiority. Blizzard is likely putting its programming muscle behind the OS with the largest share.

DirectX is actually a subset of OpenGL which has been rewritten for Windows. Does it mean "better graphics"? That's hard to quantify. I look at the Myst games for the Mac, and I've been impressed by their graphics. There is also Maya for the Mac which has incredible shadow effects which can be created on the Mac for movies. For all intents, Blizzard needs to contact Apple Developer relations to learn more about how to optimize their software for the Mac so people aren't complaining. One thing that is making it hard to convince game developers this is worth the effort is that Macs now have the ability to run virtualization such as Boot Camp, VM Ware and Parallels in some cases with graphics drivers which are native to Windows, and thus make it hard to justify making both a Mac and a Windows version. Get together all your Mac friends to write a petition directly towards Blizzard. Petitions on this board aren't allowed, but if you know some who really want better games from them, they are the ones to write.