How many films had 4 sequels?

Here is a short list :

3 Ninjas

Airport

Lethal Weapon

The Magnificent Seven

Anaconda

Meatballs

The Mummy

Bloodsport

Bring It On

Die Hard

Rambo

Doctor Dolittle ( 3 and 4 was direct to video)

The Exorcist

Species ( 4th was direct to video)

Jaws

The Karate Kid