As problematic as 'The Lost World' may have been, it did expand the horizons of the Jurassic Park universe, 'Jurassic Park III' was a huge step backwards. The characters are sub-standard, the story is lazy and shamefully contrived, and the effects aren't as good as either of the previous movies, almost seeming to be a parody of a Jurassic Park film.
The plot, as thin as it is, centres around the rescue of a boy named Eric who ended up stranded on the now restricted Isla Sorna, and the survival of the rescue team led by Alan Grant. Alan is lured to Isla Sorna by seemingly rich businessman Paul Kirby on the promise of cash to fund his dig. The plane lands and Amanda Kirby, Paul's wife, attracts the attention of Spinosaurus which causes the plane to crash and devour members of the crew. The rest of the movie is a series of chase scenes involving the Spinosaurus and the Velociraptors, interrupted by cloying domestic drama between the Kirbys reuniting with Eric and coming back together. The climax itself is unsatisfying, requiring a military deus ex machina that just feels tacked on.
In all fairness, Sam Neill does a good job at bringing a jaded Alan Grant to the screen, working with what little he had. But his character is ruined by undoing his arc in the first film about learning to love kids and marrying Ellie, here Ellie is married to another man with two children. The writers could have prepared something special involving Alan and Ellie's relationship and their place in the world with live dinosaurs on the planet; it was insulting to undo all that development. His scenes in the prologue had potential, showing Alan's struggle to keep palaeontology alive and rekindle his love of dinosaurs. But it all amounts to nothing.
The film has only a few worthwhile action scenes, specifically the Raptor attacks and the group's encounter with a colony of Pteranodons in a giant aviary, a memorable scene conveyed with an eerie and mysterious atmosphere. Some of the musical cues are melodic and charming, but I yearn for John Williams's talent. At times, the visual effects for the Raptors are actually quite good, but the rest are incredibly rushed and don't allow the audience to soak it in like in the first film.
Due to the weak writing and wasted characters there are the many stupid moments throughout the movie. Barely twenty minutes into the film, Alan has a dream about a talking raptor on the flight to Sorna, it's intended to be scary and foreshadow the Raptors' capability of speech but it comes off as childish and goofy. (Real life raptors weren't even capable of human-level speech patterns). The ever annoying Amanda Kirby seems to exist only to scream, bicker and run away, never contributing anything but maudlin or moronic moments. William H. Macy is completely wasted. The rest of the characters are bland and forgettable. Some outright stupid moments include a satellite phone being heard from the belly of a Spinosaurus, said Spinosaur is shown as being able to break a fence designed to contain dinosaurs yet cannot break down a rusty metal door, a ridiculous cameo of Barney (I wish I was joking!!), and a cheap regurgitation of the dino dung scene from the first film.
Even the dinosaurs themselves have been ruined; the CGI herbivores are pushed to the background with little screen time, and the carnivores don't behave like real animals, like in the previous films. The animatronics are clunky and the CGI is too obvious. The movie tries to recreate the sense of awe and wonder from the first film, but it feels forced and artificial.
The most obnoxious change is the addition of the Spinosaurus. While I accept that it was larger than T-Rex, Spinosaurus was not a rampaging movie monster that hunted human-sized morsels like a serial killer. This leads into the infamous duel between the Rex and the Spinosaur, and it's a problem because the T-Rex was an integral part of the previous films and a childhood favourite. The fight itself was overly brief and anticlimactic. The T-Rex was set up as a predator with both ferocity and nobility, having it dispatched in such a way feels like a cheap shot. It was just a botched attempt to showcase a dinosaur that hadn't earned it's stardom like the Raptors.
What frustrates me the most about 'Jurassic Park III' is that there was potential to make up for some or more of the shortcomings of 'The Lost World'. Instead it's the shallowest and the least adventurous film of the entire trilogy, there's too much focus on the domestic drama. While the first two films dealt with themes of science, technology, playing god, and man vs. nature, 'Jurassic Park III' took the franchise away from exploring such themes, choosing to be safe and marketable and lacking in substance.