That's why I considered it a failure; by Valve's standard. I played CSS until CSGO, that's 10 years, and it's still widely played. I played Half-life deathmatch for the longest time, I can't even remember for how long. CS 1.6 for at least 6 years, and there were always people and it was always fun (except the few games where teams were stacked on CS, but even then, it was generally fixed quickly). L4D2 is 4 years old and 3 months, that's not more than 5, and the failure of Versus is what I am surprised in Valve. But then again, they knew they fucked up, they released L4D2 way too quickly, had to issue a bunch of apologies because for the first time in history, the confidence in Valve was shaken, people saw it was a cash grab ala "One COD every year!" and on release, it was kinda lackluster, it was basically nothing more than an expansion on top of L4D, so people wondered why make another game and not an expansion.

It kind of reminds me of CoD actually. Except for CoD4, which remains pretty widely played, when a new CoD is released, the population is decimated on multiplayer as everyone moves on to the next. If the next game is a failure, players don't return to the older games, they just leave to ANOTHER game. That's what happened to L4D2. There were other details, the 4 characters of L4D were iconic, they left an impression, you liked them, you wanted to know much about then. The athletic girl, the war vet, the black white collar and the renegade dude, it just made for a perfect match, and perfect atmosphere.

Meanwhile, L4D2's survivors were really, really lackluster, their interactions were weird, it didn't feel as cohesive and that was another part that took me away from the game.

I take this on a personal level because I REALLY liked L4D, but L4D2 ruined the series imho, Versus being a thing of the past, and people don't really wanna run back to L4D, because you don't return to a dead game.