PC doesn't offer just better controls and graphics - PC gives you the means to test your skills without limiting you. What the consoles' gamepads do is limit everyone's skills/accuracy and then adding auto-aiming to give you the impression that you're doing it... but really you're not giving much input, and you're not able to show your skills at a higher level.
Left 4 Dead is a good example. I heard that the X360 version at highest difficulty is comparable to the easiest setting of the PC version lol. How lame is that.
PC also gives you another big thing: MODS. MODS, MODS, MODS and more MODS!! They're awesome.