The New York Times on Sunday published a story called, PC Games, Once Down, Show Signs of Rebound. It is a well-written and informative piece detailing the current state of PC games.
If you've been out of it, PC games have taken a back seat, and lost shelf space, to console video games. That is starting to turn around due to a multitude of factors including: PCs can more quickly adapt new technology, PC games tend to be less expensive, World of Warcraft continues to sell like hotcakes, and Microsoft's push to standardize PC games (Games for Windows) so that you'll know what game will play on your PC.
Let me add to that my feeling that a lot of thirty somethings, who grew up playing PC games, are very comfortable with PC gaming. Since they already have a PC, the entry cost to re-enter the gaming world is simply the cost of a game, rather than having to buy a new console.
The article is very interesting and I highly recommend giving it a read.