So here's the lucky four:
First winner: #101 (k0nk0n)
Second winner: #117 (Skram)
Third winner: #48 (SirGray)
Fourth winner: #38 (Clown069)
Hopefully I didn't make a mistake somewhere. I'll be sending out PMs to each of the winners soon asking for a list of their most wanted - least wanted game in my inventory and take it from there.
Thanks to everyone who showed interest, too, and sorry that I didn't have more to give out. I may try to give away more stuff eventually, possibly even some physical media and Team Fortress 2 items (you don't want to know how much I've scrounged up over the past three years). Bet you're psyched!