CS still has one of the biggest followings of any games out there, is this why?
1. It requires so little resources that we have been able to install it on the laptops (old) and desktops (older) at work. To drive back from Midrand to the south in the evening at 5 p.m. is a nightmare, so a few cans of your drink of choice (no alcohol at work though), some chips and five other players = fun times.
2. It is a simple enough game to learn, so someone new to the genre can start here and have fun. Then these players can progress to the more difficult and challenging games.