It's not just that PC is an upgrade (it is in every imaginable way by a factor of 2 just to clarify) but it's also the fact that you can continue to upgrade components of your PC as necessary. Resolutions are starting to go up again and quite frankly, by the time the next-gen consoles are out and ready to brag that they finally have true 1080 graphics (which PC's have had for years), there's a good chance people might be playing more commonly at 1600 resolution.
Consoles will always be behind the curve. The only way for consoles to get ahead in the game market would be for developers to simply abandon PC gaming entirely, which they won't. For all the shouting about piracy that goes on with PC gaming (and goes on with console gaming as well), PC is still extremely profitable due in part to the fact that a person who builds a $1000+ gaming rig is probably the kind of person who can afford to buy a fair amount of games on a whim.