242 games, of which I've completed around 35, and played another 50-70 to satisfaction. Like many others here, I am a bit of a bundle enthusiast! Some of the games were completed on another platform than Steam, though.
A thought for the originall post: why not add a question about the best and worst purchases we've made there? For me, the best was probably The Binding of Isaac for 2 Euro (152 hours played), and the worst was Arkham City for 40 Euro (8 hours played, and I know for a fact that for some of them, I had the game running in the background while I did other stuff).