This is by no means a comprehensive list, but it's not a bad yardstick for franchises that have escaped the easy three-movie structure and tried to sequel a little closer to the sun. As it were.
List by Tony Hightower Pro
Fourquels: When 3 Isn't Enough
It was the fourth Star War that was produced. If you wanna well-actually me and say A New Hope belongs here instead, well, I get it.