So Valve made three big announcements last week. (Well, two big announcements and a foregone conclusion.) They announced a new operating system, a new console on which the OS will run, and a new controller. Having the biggest name in PC gaming move into the console space has ripped open the embarrassing PC vs. consoles debate again, and people are denouncing or praising the Steam Box based on which camp they're in without really understanding what it is or why this is such a completely fascinating move for Valve to make.
So let's get this PC vs. Console thing out of the way: On the consumer side, the debate is about which games you like more, controller setups, convenience, and pricing. The debate is still very much alive and no single gaming device is objectively better than the others. It depends on how you play, why you play, and where you play. There really is no clear winner.
But on the corporate side, the debate has been over for almost a decade, and consoles won. It wasn't even close.
To the big companies, "gaming" means big-budget AAA titles. They want to make big, big games and sell them to as many people as possible. That means selling to console players, because AAA console players vastly outnumber AAA PC players. (Well, you sell more units. Let's not drag piracy into this. It's complicated enough already.) The mobile market is shaking things up right now, but it's still true that if you want the big bucks and you're not World of Warcraft, then you need to be on consoles. Mouse and keyboard controls don't matter to the likes of EA and Activision. They also don't care about the price of Xbox LIVE, strategy games, indies, graphics cards, modding, or any of the other stuff that's so important to us PC gamers. They care about sales, and consoles far outstrip the PC. This is a simple business decision.
Which brings us to Valve. Now, you can argue that Valve is an incredibly smart company or you can argue that the competition is just shockingly inept, but the dominance of Steam can't be overlooked. I have no hard numbers on the market penetration of Origin, Games for Windows LIVE, Direct 2 Drive, Gamer's Gate, Origin, and Good Old Games. In fact, I don't think anyone has the complete picture of what people are using. But just think of how often you see people ask, "Will this game be on Steam?" Compare that to how often people ask about (say) Origin or Uplay. Have you ever heard of anyone asking about the latter in a hopeful way? I haven't.
I don't think it's unreasonable to say that if you were to combine the userbase of all non-Steam digital gaming / distribution platforms and then double them, it would still be less than the number of people using Steam. Since 1990, I don't think any single console has dominated its rivals the way Steam has dominated the PC world.