Just browsing these comments shows me that (as usual) everyone is overlooking the true killer feature of PC gaming, and the reason why, assuming enough corporations get their shit together, it can take over:
The hardware is basically free.
You already own a PC. Everyone does. It isn't like consoles where you have to spend $400 dollars on specialty hardware. You don't have to purchase gaming hardware, because you already own the hardware. Please read the rest before you flame me.
There is this weird notion that you need crazy top of the line hardware to play games. That for some God-given reason gamers need to upgrade graphics cards every 2 years. It is just assumed to be that way because that's the way it's always been. Well actually it's a pretty recent thing.
Before 3d, any somewhat modern PC could play any modern game. The original Doom, for example, ran off of anything. Point and click adventure games ran off of anything. Heck, going back all the way, text based games ran off of anything. This premium hardware BS is a fairly recent thing. I'm not sure if Myst or wing commander is to blame, but the culture of 'graphics first' grew to define the PC gaming world. And it's killing PC gaming 10 times faster than piracy ever could.
But according to this article (and what I've known all along), graphics aren't going to be the driving force behind the games industry going forward. Community based games, perhaps even browser games, will dominate, quickly eliminating the PC's two biggest impediments: piracy and the graphics culture.