I believe there is a vicious cycle that is occurring in PC gaming with the AAA game developers and publishers (Ubisoft and Rockstar come to mind) where PC ports will often be available a significant amount of time after console, or be of shoddy quality, or both. Perhaps as a consequence, PC sales are weak. And because of weak sales, there is less incentive to really push for simultaneous PC release for games or at the level of quality and polish that PC gamers demand, possibly affecting sales again.

I'm not sure how accurate pre-orders is as a sign of platform popularity, but with Assassin's Creed 3, (and if the numbers are accurate,) it seems like PC only makes up about 9%~ of pre-orders[1] with the rest being dominated by XBox 360 and PS3. That's an incredibly poor number to justify any sort of effort in PC gaming.

But of course, there are so many variables at play that these numbers could mean almost anything. Heck, I could even attribute it to AC3 being far more comfortable to play with a controller/console than a keyboard/mouse. And of course, they did release it 21 days after the console, so there's that.[2]

[1]: http://www.vgchartz.com/article/250519/usa-preorders-chart-2...

[2]: http://assassinscreed.wikia.com/wiki/Assassins_Creed_III