Its hard to say, JP1 is an absolute masterpiece. A perfect blend of science and fiction. Something that the other movies never came close to. After JP1 it was all just 'GRRR DINOSAUR EAT MAN GRRR' and not the science behind everything. There is three scenes in particular in JP1 that really stand out.
-
The lunch scene where they discuss the potential pitfalls of the park, especially from Dr. Malcom. In fact the worst part of this scene, and ironically the part that's supposed to hit hardest for the uneducated, is Dr. Grant's retort at the end of this scene about not having the slightest idea what to expect by throwing dinosaur and man together. Regardless the scene is BY FAR the best scene in the movie.
-
The scene involving the lysine contingency. While the science mentioned in this scene is pseudo-science at best, it at least provide a glimpse into the thinking behind the park, the engineering of the dinosaurs, and the potential steps taken to mitigate damage should the worst occur. Something that you NEVER see again in any JP movie. While the engineers did have this thought in place, their hubris still allowed them to create something that should have never been created (see the Lunch scene).
-
The scene between Hammond and Dr. Sattler regarding Hammond's decision to create the park. He wanted to bring joy to the world, and even after all that has happened so far (his own grandchildren being lost with escaped dinosaurs), he was still deluded into thinking the park could work. He had a conviction that he wanted to realize, but everything was working against him. While this Hammond is VERY different from the Hammond in the book (a complete asshole who got his comeuppance), it provided great character depth on how far this man wanted to go to achieve a dream.
JP1 had the benefit of having Michael Crichton himself involved in the screenplay and I really think this helped bring the science aspect forward. Something that was unfortunately lost with the sequels.
Its sad that Spielberg approached Crichton to write a sequel to Jurassic Park (novel) so they could make a sequel movie, which he then did, and then the movie ended up being completely different. Though, the sequel novel isn't much better to be honest.
If I were to rank them:
JP1
The rest are terrible movies that just want to show dinosaurs attacking people