Got anxiety issues? Don't read on. Seriously, go read another article. For those still reading though, here's something neat: there's now a website which will predict how many hours worth of game you've got piled up in your Steam library.
SteamLeft compiles data from HowLongToBeat.com–a database compiling estimated game length for thousands of titles–and then applies that to your Steam account. If you're sure you want to be privy to this information (and I know I don't) then you can check it out here. It also advises what you could be doing instead of playing those games, for instance watching Avatar about 500 times. There was a similar website for calculating Steam playtime a couple of years back, but its since been removed.
Let me know how many hours you've got left in the comments. In the meantime, here's a meditation on the pile of shame and some potential strategies for battling it. If you're anything like me, you'll simply ignore the pile and play Spelunky instead.