When we read these reviews we see a mixture of those greatly appreciative of this film, and those who consider it garbage. To the later I can only guess two things apply:
1) They are not aware this is PART 1 of the movie. More to come.
2) Some quite likely don't understand the Japanese mentality or the Godzilla mythos. In such case this will make no sense. Those who understand both Japanese cinema and the Godzilla mythos understood this film and rated it highly.
First regarding the film itself: animation was top-quality, with an excellent mix of anime and realism with computer graphics. The blend is fairly perfect, so much so that one forgets we are watching an animated film-- until something strikes us as particularly well-done.
The story line and plot-- and even the very final after-credits scene-- contrary to some claims makes perfect sense, is consistent and follows a logical flow. It is a well-done story... and I am very critical of films with lousy stories and plots. Of course to understand, one has to understand Godzilla. If one thinks Godzilla is just a "scary monster" or a dinosaur on steroids, they have no idea what Godzilla really is.
So considering the terrific animation, good voice-over acting, well-done story line and consistency with the Godzilla theme, we have a real kicker of a Godzilla movie... one of the best I've seen. I tend to be very critical of movies and don't cut them much slack in the case of sloppy production. This was done well and is definitely worth watching... unless of course, one understands zip about Godzilla. It does help to be acquainted with the concept going in.