The simplest, therefore, the greatest of First Person Shooter games. Two teams, Counterterrorists and Terrorists, going at each other where the end result is that the opposing team is splattered across the map and your team is victorious.
Unlike most FPS's these days, there is still unlimited variety in what modes and maps you can play on CS. Unlike the media-hyped CoD, Halo, etc other series, there's more innovation and imagination in making and playing CS instead of just glitching and recording worthless kills (*Cough machinma Cough*).
No automatic knives once you get close enough, no dumb killstreak rewards that does the killing for you, no vehicles that run you over, no power armor. Just you, your weapon, and an instinctual gauge as to what is a successful shot.
Like ANY other game, you have to play it REPETITIVELY in order to be good.
CS is also a good example that Realism =/= Quality Gameplay
Contrary to new (raging) players belief, there are more 12 year olds and campers on the newer FPS's than there is on CS.
CS 1.6 have smaller killboxes than CS:S and therefore requires more skill
Person A: Look at my score in Black Ops, 300-16, I'm so good and I only had to use chopper gunner twice. Look at me knife, so pro
Person B sits Person A in front of Counter-strike 1.6 and directs Person A to play
Person A: OMG WTF, these KIDS are hacking, how the fuck is that possible, this is a gay game, where are the care packages? No sprint?!?
Person B: *smh*