Some people may have noticed that I did not mention the PC as a game console. The PC has quite a number of games for it, but suffers from one major problem: too much hardware variation. When you are developing a game for a console, you know exactly what hardware is available and what the limits of the system are. With a PC, every single model has different specs and their are many new models every month. If you add custom built machines to that mix, well, it is a nightmare. Sure, theirs the minimum hardware requirements stickers on the boxes, but only geeks (like me) can understand those.
The worst part of PC gaming is the simple fact that most machines do not come with adequate video cards for handling high end games. In order to play the latest and greatest games on your new PC, you either have to buy a premium model or upgrade your video card. A high end video card will set you back the same amount as it would cost you to buy an entire game console.
Another major factor going against the PC as a game platform is the piracy issue. While it is possible to pirate games on any of the consoles out there, it is non-trivial. PC game piracy, on the other hand, just requires knowledge of where to download the cracked versions of games from. As a result, piracy is very high so a lot of game developers are moving away from PC development. With consoles starting to let more independent developers develop for their systems, even indies will start to move away from the PC platform since people even pirate indie games.