It has to be a tie for me between the first & second ones. The first one just gets you into a brand new world of dinosaurs & how they came to be. The 2nd one fills in some gaps. I was not impressed with latter ones. I felt they waited too long & the newness of this storyline lost its appeal.
The first one was the only one I enjoyed and was amazed with how cool it was when I was kid. I was 7 when it came out. I didn't care for the rest of the movies that followed. They just didn't have that same magical effect that the first one had on me.