Well I was a PC gaming fan for a few years (I played Call of Duty UO constantly and was a member of the great clan BW-UK)
I have now got an xbox 360 and have let the PC go for a while. For me, the 2 formats maybe should not be compared too closely as the experience seems completely different. My PC gaming was dedicated to One Game all the time. The clan involvement was large which gave the game a Modded, very personal feel (there were all kinds of mods and custom maps which were not part of the original game) Intense may be the word I suppose
Now, I have moved downstairs to the easy chair, hung up my keyboard and mouse and moved to are more laid back form of recreation (Please dont jump down my throat at this, it is MY opinion and may differ from yours) I play games I never did on my PC such as kameo and PGR 3. As for Call of Duty 2 on the 360, I havnt bothered. For me,(once again my opinion will differ from yours) the Game in its present form cant compare to the 50+ player servers, mods and the Keyboard/ mouse control I enjoyed as a PC gamer. By the same token, sat in my office playing kameo on my PC would never be the same as sat downstairs in front of my LCD TV in an armchair with a wireless controller in hand.
What Im saying is that one format is no better or worse than the others...at the moment. If the Xbox 360 afforded keyboard/mouse control (if like me you cant get the hang of Joypad for FPS), dedicated servers (and server admins with server control such as kicking), there might be a different story...