25 of 26 games in the major advertising space on Steam front page are Mac compatible.

Just think about that for a moment. Compare that with 2 years ago. 

Mac is still lagging behind in many ways. It still takes 3-9 months for AAA game to come to Mac, if they come at all. But Civilisation V, Arma Tactics, Borderland 2, Bioshock Infinite and Batman Arkham City are all Mac compatible.

Linux is still lagging behind a bit, but it it’s definitely catching up as well.

Windows and Linux comptuers will have an advantage over Macs in the gaming space as they allow for modification, letting you build your own computers with powerful discreet graphics cards for high end gaming. Instead of replacing an entire computer, you just replace the piece you want to upgrade - a direct contrast to upgrading your iMac or MacBook Pro. 

I don’t expect this to change for Macs. I think Windows computers will continue to be number one and I would not be surprised to see Linux gaming overtake Mac gaming in the next 5 years. But Mac gaming is not the total shit-can it used to be.