Those were retail sales. Most pc gamers buy games digitally nowadays. Hell I can't even remember the last pc game I bought in a store.
I read an interesting article that predicts PC games will outsell the console market within the next 2 years. However, what we pc gamers will get might be horrible ports. Rumor has it the next-gen gaming consoles will be far inferior to pc's compared to current gen when they premiered. That certainly won't help matters.
Like I said before, don't look to AAA game developers to bring us something great and innovative, its more likely going to come from indie game developers.
http://wraltechwire.com/business/tech_wire/news/blogpost/10174154/