I am incredibly annoyed at this movie's reception. It seems to get a pass because of its animation (which is good), but the characters are flat as hell.
One of the "kid power" movies of the 1990s. What separates this one from the others is the edge it has compared to the other movies from that era of Disney family flicks. These kids do genuinely talk like middle schoolers do, and their sense of solidarity come across nicely. Also the goofiness of Ben Stiller's Tony Perkis and Lars gives it an additional sense of goofiness that's a pleasure to watch.
The downside of the film is that it does stick to the same plot mechanics of similar movies. There's even a competition at the end for the sake of the formula.
I've obsorbed this plot before via an episode of the magic school bus, yet I was still eager to go along with the perils of the journey and marvel at the scenery of the human circulatory system. I gotta give the color photography it's due here for making the scenery pop, along with the psychedelic footage of red blood cells. Even though you can see how the sets were conceivably constructed, it doesn't take away from how well done they…
What I liked most about this movie is how well the dystopian society of Mexico is made to look. Maybe because aside from monsters, it really isn't all that much different. I could see an argument that Monsters is a movie about the country's drug war, though you'd have to forget about that ending.