Make your own fun. It's a lesson that we sometimes forget in the glut of linear, Hollywood-style "cinematic" games.
I once spent an afternoon among friends in Ultimate Spiderman seeking out the highest building in the game, climbing to the top, then leaping off, free falling until the last possible moment before doing a web zip to save Spidey from being smushed. It turned into a competition to see who could get nearest to the ground. It was fun.
Now I want to mess around in Grand Theft Auto V some more. I haven't done a single story mission.