Personally I enjoyed Jurassic Park III more than I did The Lost World, but the original is the best by far.

The introduction of Spinosaurus Aegypticus in the third installation was off the beaten path a ways, as in the previous movies we saw Tyrannosaurus Rex terrorizing the characters. The new big and bad dinosaur worked for the movie though. Althought some scenes with the animatronic Spinosaurus were cheesy, the CG clips of him were incredible. Combined with a great score (as always) and the eye candy of new dinosaurs, Jurassic Park III was a thrilling, successful film in the series.