The best multiplayer game ever and almost certainly in the top 5 greatest games of all time.
What's so good about CS? Well firstly there's always a goal to achieve which means working as a team is essential and secondly because you have just one life, if you die you wait until the end, it means each kill has value and really gets that adrenaline pumping and pulse rising when there's a fire fight. No other FPS game has ever beat that feeling of being the only man left on your team against 3 others and you take them all out through skill and cunning. It's like football (soccer), people say it's boring because there are never any goals but that's the whole point. When you do score it's such a massive buzz when you know that goal could be the winner.
I would say the game is certainly in the top 5 greatest games of all time and for me in top 3 games of all time and I've been playing games since the 70s.