Even though I don't buy that many games on Steam, I eclipsed my X360 digital library in like 2 days lol
My total game count on Steam is around ~64, but that includes all the little packs and DLC that counts as separate titles for some reason (Valkyria Chronicles counts as 1 title and 4 "DLC" titles). The actual number is probably around ~50, but still higher than my 360 library.
As I get ready to sell my 360, it makes me sad that there are digital titles that never came to Steam, like Puzzle Fighter HD, SF3: Third Strike Online Edition, Darkstalkers Resurrection, Scott Pilgrim vs. the World, etc. They deserve better than to remain on a dying console.