DOTA 2 and Counter-Strike: GO combined are bigger than all of Steam was just 2 years ago.
http://www.pcgamesn.com/dota-2/dota...am-was-two-years-ago-and-theyre-still-growing
I get DOTA. It's free to play and MOBAs are exploding. The way Counter Strike (and now CS:GO) remains on top of the multiplayer shooter genre on PC has always kind of been a mystery to me though. It's not free to play, there are a million multiplayer shooters, and graphically it's pretty dated at this point because its 3 years old and even back then it was designed to run on light hardware.
I never had a gaming PC when the original Counter Strike was huge and I didn't have one yet when CS:GO was released so maybe I just don't get it. My only experience with Counter Strike was the port on the original Xbox. That was my first Xbox Live game and I played the hell out of it. I had my custom soundtrack saved on the Xbox hard drive and I probably played more hours of that than any other game on Live for that system.
From my time on Xbox I know that Counter Strike is more tactical than most other shooters. You don't just run around like crazy because you don't respawn and it only takes a bullet or two to kill you. If you rush in and die early you hurt your team because then they are short handed for the rest of the round. Maybe that's where the appeal comes from? Still, with all the shooters on the market it seems like something would be able to knock off a 3 year old game.