Which RPG have you owned the longest but not played?
Stars Without Number from Sine Nomine Publishing written by Kevin Crawford is most definitely the one I've owned the longest and not yet played. When I was first getting back into RPG's over five years ago, I picked up this free version of the game. I think I fell in love with this game when I saw the RollPlay Swan Song Youtube video live play by itmeJP. Adam Koebel did a fantastic job of bringing his version of the game alive. I've always been a sucker for science fiction and this one really struck a nerve with me. If your'e not familiar with it then I suggest you at least get the free version here and read it. There is also a Kickstarter campaign going on right now for a revised edition which I am a backer.