I've got that exact problem at the moment. Come back to a game after a couple of months and can't remember any of the controls. Personally, I suspect I'm not into gaming as much as I used to be.
My favourite used to be playing games with mates taking a turn every time someone died and getting through games that way. Trouble is, since most of them and I are married it just doesn't happen any more. When I was a student the playstation just seemed to be on all the time. Someone would come back from lectures and someone just leaving would hand them the controller.