I hate to be a downer, but...this actually isn't impressive. In fact, it's kind of disheartening if this is the future of PC gaming. These sales numbers are pretty awful.
Blizzard/Stardock games excluded, I think it can be agreed that Steam is the primary source of hardcore game purchases. Sure, retail makes up some hardcore purchases, but generally the majority of retail PC game sales constitute casual games.
That said, the top selling game on Steam for the year sold 1.6 million copies? That's it?
It was announced about a month ago that Black Ops had finally made $1 billion in revenue through the console and PC markets combined. It only made $96 million on Steam. That's less than 10% of the game's total sales. Or, in the eyes of a publisher, a relatively safe market to ignore in the future. And, keep in mind, that was the highest revenue earned by any game on Steam!
Obviously, that's a console-focused title, so that shouldn't be used as a primary example. But still, 180 games earning $1 million in revenue total is kind of scary. Many people's first thought is, "Wow, 1 million dollars? That's a lot!" For you, it may be. But keep in mind that said $1 million likely has to pay for development costs, as well as the salaries of every employee in a studio for, say, two years. Divide $1 million over 20 people for a game that took two years to make, and you're barely getting by.
I should clarify: I love PC gaming, and I'm not bashing it in any way. I'm just surprised at the overwhelmingly positive response to some very negative information.
