Alarien said:
You also don't have to deal with the higher specs/capabilities of a PC, which can run games faster and at higher resolution, meaning the expectations of PC gamers is higher.
This is definitely a bigger factor than most people realise, if you have a gaming pc, try a little experiment. Temporarily replace your monitor with a big 1080p tv (i did it with a 40inch one) although it's an experience, especially an FPS, you also realise pretty quickly that it's very, very low resolution for the size!
It usually boils down to a matter of taste in games, some are inherently suited to PC's and some consoles. FPS games, and RTS games are generally unsuited to consoles, and before you whip the halo card out, there's a lot of fudging that goes on in the background so that it's actually possible to play it with a control pad, from 5-10 feet away, as an analogue stick isn't nearly accurate enough on it's own. On the other hand, platformers, driving games, beat em up's, etc. are usually unsuited to pc's, even if you get a gamepad, you can't really get a group of people sat around playing them together.
As has been said, a lot of it is cost/benefit as well, if you develop a game for all 3 systems, you have to make sacrifices somewhere, on all 3 platforms, to make it work. If you develop specifically for one platform, you can get the best out of a game and the hardware, but you need to spend a lot to port it to the other systems properly. Going from 360 to PC gets away with this somewhat, due the common API's and the generally greater resources a pc can throw at a game.