I think there are two distinctly different RPG Genre of play that fit well in a limited number of sessions format. Knowing in advance that you are going to have a set number of sessions for your game I think Horror and Suppers are the best go to types of games for a set number of sessions.

When you are looking at Horror games you can use the first game session to introduce the story and connect the players to one and other. After you have accomplished this you can go into a Three act story arc with 3 sessions per arc. Providing you with a great outline to how to set up and run your game. This format holds true with Super hero games as well.

I find I like setting session limits on games of these types due to the fact that often after 10 or more sessions in a Horror game the fear begins to fade. And in a Supers game, the heroes begin to grow in power to a point where the storyteller and often the players begin to bore of the setting.