That's sort of unfair, I think. Off the top of my head, there was the new Counter Strike late last year, Portal 2 the year before, plus the level editor/sharing update last year, DOTA2 in beta at the moment, constant updates to TF2, recent OSX and Linux ports of most Valve games and Steam, the Source engine and related tools, the Steam Box project, the mod workshop for some games, Steam Greenlight, and whatever games they've yet to announce still in development.
Considering Valve Corp as a whole supposedly has a total of only about 400 employees and is acting as a developer house, publisher, and 3rd party distribution system rolled into one, I think they've got a pretty fantastic churn rate.
EDIT: Just want to say I wasn't the one who downvoted you.
Hey, I do not mind being downvoted anyway. I stick to my opinions no matter if they are unpopular.
I know what you mean, but apart from Portal 2 the rest does not really qualify from development from scratch (even Portal 2 is dubious on that aspect, since it takes all the mecanisms from the previous games and expands on it). While I love what they do as a distributor and very much appreciate what they do for Linux support, as a pure game developer they fall short of expectations, and they have not done anything very original for a while. For a company with a "flat organization" that is somehow disappointing.
They do use outside staff for development, at least in some cases, so perhaps talking about the 400 employees is a little misleading. For example, Hidden Path Entertainment did a lot of work on the new CS title, and Wikipedia tells me they also did some models work on Left 4 Dead 2. I've no idea about the other games, perhaps they are all done 100% in-house.
Considering Valve Corp as a whole supposedly has a total of only about 400 employees and is acting as a developer house, publisher, and 3rd party distribution system rolled into one, I think they've got a pretty fantastic churn rate.
EDIT: Just want to say I wasn't the one who downvoted you.