I don't know why, but I sometimes do. I've had a copy of Bujingai and Crimson Tears sitting there for a week and I haven't touched them, and in the last year I still haven't even opened a ton of games like Armed and Dangerous, Prince of Persia, Metal Arms, and Deus Ex: Invisible War. Yet I played Metal Slug 3 for like ten hours after getting it, and still play an obscene amount of Devil May Cry and Gunvalkyrie.
Anything similar happen to anyone else?