There are some striking similarities between the new adversary in this film and that of Gamera 2: Attack of Legion. Both are insect-like monsters that initially swarm as more or less human-size creatures before later revealing a giant form to battle their respective kaiju counterparts.
While it would have been poetic justice for this film to steal from Gamera, I doubt that was the case. For one thing, this movie was released seven months earlier. It does however, "draw inspiration" from elsewhere:
Movie: the soldiers enter the pipe-filled industrial site, moving in teams. They carry assault rifles and flamethrowers, and each team has a heavy weapons trooper with a harness-mounted minigun
Me: "Gee, could you be any more obvious with your Aliens riff?"
Movie: one of the soldiers has a motion detector
Me: "I guess that's a yes, then."
Later, it emerges that the the Destroyah beasts even have the mouth-within-a-mouth thing going on, though frankly, they're considerably less terrifying than everyone's favourite xenomorph.
So, setting aside the similarities with other movies, how is this one? Well, it's okay. If you're not into kaiju it's not about to make you a believer, or anything like that. And even if you are a fan of the genre, you're probably going to roll your eyes at the human-centric portions of the flick. The Aliens scene is pretty effective but other than that they're almost all exposition/narration fests, much of them coming from a college student who somehow becomes the #1 authority on all things Godzilla about five minutes into the film.
It's a weakness of the film that all the exposition and narration is actually pretty necessary. There's a lot going on here: Little Godzilla growing up. Adult Godzilla blowing up. Monsters from the Pre-Cambrian being released and mutated by the weapon which destroyed the Original (1954) Godzilla. It's all driving toward what's clearly intended to be an "epic" conclusion prior to the franchise taking another hiatus.
I'll give the film points for aiming for something a little different than usual, but for my money it didn't quite hit the mark.