I've always regretted buying Morrowind. I just don't see how people ever enjoyed this. Maybe I need to try it using mods or something, but as it is it just feels like playing an MMO...by myself.
Aside from that I have a good sized stack of crap I doubt I'll ever touch, but most of those were old and cheap impulse buys from used game stores, I doubt I spent $100 on the entire pile.