that all have the same director. Thought about this the other day and could only come up with a handful since it seems like having 3 or more sequels is tough enough, but all the same director, that's just crazy.
Steven Spielberg - Indiana Jones 4
Richard Donner - Lethal Weapon 4
George Miller - Mad Mad 4
Wes Craven - Scream 4
Don Coscarelli - Phantasm 4
George Lucas doesn't count since he directed 4 but not all 8.
Possibly Peter Jackson with 6 but is it considered two separate trilogies or is Lord of the Rings sequels to the Hobbit? I don't know. Are there any more of these guys?