I own a PS3, a Wii, and my hand-built two-years-still-strong gaming rig.
With a few exceptions, PC games tend to be much deeper than console games. You don't see stuff like GalCiv2 on consoles. But consoles get a stronger lineup in terms of arcade-y action games (with the exception of FPS).
And then there's Rock Band, of course.
I find that if I have 20 minutes to drop a quick game, I'll boot up my PS3 or Wii. If I have an hour or two, definitely PC games of various flavors.
Two other HUGE bonuses to PC gaming:
1) the really old, classic games? They probably still work. Not too long ago, for example, Tribes2 was relaunched - free to download, free to play, free free free - as TribesNext. Who doesn't miss skiing, really now?
2) indie devs? They can actually get stuff launched on the PC. I don't just mean StarDock, I mean the guy (essentially the one guy) who made Mount&Blade, for example, or the guy (the one guy) who made the Out of the Park Baseball series...