What is it that makes a game particularly memorable?
When you finish a game, you want to feel as if you’ve accomplished something. By the time you beat some games, you want to really feel you’ve made the game world a better place through your actions (or, perhaps, you have intentionally left a horrifying wake of devastation). You’ve solved all major problems, and probably a lot of minor ones as well. Maybe you’ve beaten a particularly tough platformer or shooter and you feel like you’ve done a superhuman feat or twelve. The important part is you feel like you’ve done something significant or participated in a memorable story. The main pieces used to bring about this feeling are plot and challenge.
Unfortunately, this sense of accomplishment can be out of reach when playing a game. → Read Danger!