I played CS when it was the only mod around that I really cared about. It was good simple fun, but it quickly got swept away when DoD showed up. I played in the first three Battle For Europe games, and got a healthy taste of organized co-operative play (not to mention a couple of 8-12 hour marathons).
But then NS showed up. The perfect game, mixing FPS and RTS elements, and requiring true co-operation every time to win. I think Necrosis said it best, deathmatch is dull. In fact, I have more fun playing the single player elements of games, and usually don't explore their multiplay options (or when I do, they last about a week.) Why is this? Because when I do feel like a multiplayer game, I go play NS on LM!
Seriously, I've never bothered to hang at the same server before (stats=blah), but I finally found in LM the perfect kind of server. Full of talented, respectful players, and with a strong community backing, its no wonder I can't find a good MP experience anywhere else!
/gush