You realize the entirety of Valve doesn't sit on the hat certification line, right?
That's the joke.
Name some years over the past two console generations they didn't release a game and I'll tell you what they did instead.
i honestly couldn't even tell you what they've released since CS GO. I guess you could say DOTA but that was in beta for like the previous 3 years. all they did was make it public.
they have fantastic post game support which is what really matters, but i don't think you leave a studio like Volition just so you can make balance changes to Dota or CS
TF, CS, L4D, Dota. How many online games do they need? At some point they are competing against themselves.
Those games don't compete with each other.
Dota is a MOBA
TF is more of a casual class based FPS.
CS is your tactical FPS and geared more towards competitive players
L4D. I'm honestly not sure what's more popular, but it offers a co-op mode and a versus mode but separates itself from the other two FPS by having infected vs humans.
other than being in the first person perspective with guns, they have no similarities