I'll admit that I have only played CA briefy, compared to several years of playing CS, but I'm going to have to disagree with you guys on this. CA is great and all, but CS is a FAR superior game in terms of gameplay, and community.
All you need to do is refresh the server list, and see how absolutely massive CS is. There are loads of maps, with all sorts of mods to fit anyones needs, and while there are a lot of annoying people on CS, it's nowhere near as bad as your average CA pub or..Halo 3 on XBL *shudders*.
Also, the amount of people who use hacks in CS is GREATLY exaggerated, as are the number of "nerds" who play the game as well.