For me it goes PC>PS3>360 The last time I played on one of my consoles was about a year ago when I bought modern warfare 3 for ps3 but I sold it and then got it on PC. The only thing I miss on PC is the split screen co-op.
Consoles: Gaming with friends offline is best.
PC: Everything else (for me at least)
Since i dont have friends (Forever alone) i play PC.
Only downfall to PC: maintenance, you need to learn some stuff to get some games to work, while in consoles, its go go go!.
So if you are pacient, and like to get things done just right, PC is a great option.
If you are a casual gamer, that dosent have much time to lok around and waste on getting the PC to work perfectly, id say console.
Finally, if i was going console myself, id wait now for the next generation.
Getting xbox or ps now seems like a waste for me.
I prefer playing games on a PC. I never got into playing games on a console and I only played Halo 1 (many, many times) and Halo 2 (twice).
PC has more of the games I like to play like strategy and space combat sim (well, there's only one... X3 series). There's also a huge mod community for bethesda games and other games as well.
However, building and upgrading a gaming PC can be expensive especially if you want high resolution and lot's and lot's of eye candy. Plus new games always pushes the performance envelope.
As for consoles, all you have to do is buy the console and the games of course. There is nothing to upgrade. However, graphics never looks as good as on the PC and you are always playing games that are rendered at 720p and then stretched to fit a 1080p HDTV. On a PC you can get true 1920x1080 resolution or higher as long as the GPU is powerful enough to handle it.
I prefer PC though to stay current in the world of PCs is more expensive. You can generally get better look and feel and even performance on an up to date machine. The options for titles are often greater by way of mod kits and the like. However, due to the console shift and now the mobile shift a lot of studios are developing for those platforms instead with PCs really only getting a lot of attention from very large studios. The indie scene is vibrant though, just don't expect to necessarily pick up those titles in a store.