Some may argue that this is not horror but if Jaws is, this is. Spielberg staged it in the same way and made some top notch scares.
For maybe, I don't know, recently released hostages or four year olds, here is what Jurassic Park is about. A kindly old scientist clones dinosaurs to make a theme park on a remote island. As part of a soft open, he has some paleontologists, a lawyer and a mathematician come see the island along with his own grandchildren. Of course, things go wrong and the island ends up overrun by all manner of deadly beast. Put in a subplot about industrial espionage and you have a classy horror movie.
Spielberg has been adept at suspense since he put Roy Scheider out to sea. Here, he plays around with making a glass of water a T Rex detection system and having Velociraptors stalk their prey like the aliens in Aliens. Between moments of wonder, there is plenty of child endangerment and quipping to keep the mood light. While some might say this is an action adventure movie, I point to the mad scientist origins and the fate of Samuel L Jackson as exhibits A and B in the trial of whether or not this is horror.
If you haven't seen Jurassic Park, what, exactly, is wrong with you?