MacOS, PS4, and Wii have one thing in common that Linux doesn't have. They're not moving targets. They don't require a user have expert knowledge. Aside from OS X, they're dedicated to a specific purpose.
OS X has a vested interest in trying to build a gaming ecosystem to bolster Apple's sales, but the stigma of Macs being piss-poor gaming machines will follow them around for a long time to come. Most people can't see a need or a benefit to move away from a Windows PC, but it's very easy to see the drawbacks.
What the world is really waiting for is a console that acts like a dedicated PC gaming machine and is capable of playing all the same software. A machine where you can turn it on, pick your favorite game and just quickly play. Hassle free. They want the ease of a console with the power and flexibility of a PC in terms of upgrade paths and peripherals. If the XBOX or PS4 (as well as game developers) would just take the mouse and keyboard seriously you could transform the entire landscape of console gaming to be much more in line with PC gaming.