I don't know, 15 seems like a healthy amount to me. There are people I've talked with on other forums who had over 100 unplayed games and still bought more on a regular basis; THAT is excessive and unnecessary. And I won't even get into the people on a collectors forum I used to visit, because those people are borderline insane. When you have a ROOM full of unplayed games, then we'll talk about therapy. When you have a stack on your coffee table and make a conscious effort to get through them, then, well, I still don't see what's wrong about that. There are very few people I know or have talked with who don't have at least a few unplayed games in reserve, so I guess it's just normal to me.
I haven't checked your Backloggery in a while, I should look at that more often.