I used to use my Xbox for gaming, though since I upgraded everything in it, I choose PC over console if it's a multi-platform game. Though there are some MPs that I'd get on Xbox over PC...
Racingers (I've got an Xbox wheel)
Fighters (even had to set up my Xbox controller with Mugen, keyboard's too weird for me)
For RPGs I tend to prefer consoles... sure you're missing out on content but if it's a really addictive RPG you're going to be playing late into the night, it's a lot easier to curl up in bed with a wireless controller than with a keyboard/mouse, and playing PC games on a TV from far away just doesn't feel right...
I've got a PS3 & PC with Mirrors Edge and tbh I played the PS3 first thinking it would be a game better suited to a controller and big screen. Played it a few levels and it felt good I liked it.
I then tried it on the PC and wow it's way better. Graphics are better, the keyboard and mouse control instantly felt more natural and I felt I had more control over my character and what she was doing. I was able to achieve some stunts first or second time rather than repeated attempts to get it right.
I remember the same thing I had with a a couple of rally/racing sims on the PS2. They were good but once you played them on the PC I would never go back to the PS2 version.
Racing games are definitely better on the PC but I do prefer sims to arcade games that's maybe why?! And also because of my G25 wheel
It seems the more I play console games now (I've been more a PC gamer most my life, I just got a PS3 for media streaming/Blu-Ray) the more I prefer the PC to how the game looks and feels!
EDIT: One thing that really annoys me about the PS3 and the fact it's supposed to be this super awesome gaming machine is NO AA!!
All the games look like they are made from corrugated iron. I hate all those jaggies!!
Im a new owner of a PS3 (got it about 2 months ago, I wanted a bluray player and NHL 09. (Just got street fighter 4 too). My thing Is most games I want to play are PC exclusives or better suited to PC (except fighters, I dont think I will ever find a fighter better on a PC) could have to do with the fact usually you play fighters with friends easier to sit around a tv than a pc.
I'm a PC gamer all the way none of the current generation consoles interest me. I find that PC games may be much less in quantity than the consoles but is hugely superior in quality which I don't mind one bit. I find PC games tend to be more of a challenge and more complex than console games which tend to be dumbed down like the new Civilization for the consoles. The only downside is games that are go on both PC and consoles like Fallout 3 could have been more complex and be a better game overall if it wasn't made to target the console audience. I'm not saying its a bad game just that it had more potential.
I'm not into racing, sports, or fighting games so I really don't care much if they come to the PC or not. Though I must admit Street Fighter IV may be a exception. Also the only racing games I ever liked are the ones that are different like Carmageddon.
Besides having a PC is more fun anyways. I love putting together a new computer by myself. We can do a whole lot more as well while they are stuck with simply games and movies (but who buys a gaming console to watch movies anyways) We have countless things we can do on the PC and its not just limited to entertainment. We basically have a Swiss army knife while they have a dulled pocket knife.