Yeah, same here. I've decided to stop buying junk-y games I'll never play for cheap and buying an expensive game every once in a while that I really want to play.
As for selling/trading in games I've regretted? Truth be told, I don't think there's been a game I've ever TRULY regretted getting rid of. Sometimes I'll think "Oh I wish I still had X game" every once in a while (Shining in the Darkness is the most notable example), but then I think "Was I REALLY going to try and play through it?" or "Would this have gotten any playtime at all now that I've beaten it?" and it ends up being the case of No.