Dwayne Johnson headlines the action adventure “Rampage,” directed by Brad Peyton. Johnson stars as primatologist Davis Okoye, a man who keeps people at a distance but shares an unshakable bond with George, the extraordinarily intelligent, incredibly rare albino silverback gorilla who has been in his care since he rescued the young orphan from poachers.

Dwayne Johnson has become a genre unto himself. Outfit the hulking former WWE star in a pair of cargo pants and a snug henley tee, and throw him into any extreme situation — jungle-based video game, diesel-fueled car stuntery, beach crimes, fighting an earthquake, starring across Kevin Hart — and it just works. So pairing Johnson with a giant albino gorilla in the video game adaptation “Rampage” feels right. The tagline reads “big meets bigger,” and that’s about all you need to know. Johnson, who usually dwarfs his co-stars, this time gets to feel small. It’s big all right — big, dumb fun.

Directed by Brad Peyton, who has wreaked cinematic havoc around Johnson in “San Andreas” and “Journey 2: The Mysterious Island,” “Rampage” expands the narrative of the retro game, which involved a giant gorilla, wolf and crocodile crunching skyscrapers into dust. In this iteration, writers Ryan Engle, Carlton Cuse, Ryan J. Condal and Adam Sztykiel have anthropomorphized the gorilla, who is now named George (played by motion—capture actor Jason Liles), the best friend of Davis Okoye (Johnson), a primatologist with a background in the Army Special Forces and anti-poaching activism, naturally. He runs the wildlife sanctuary in San Diego, where George makes his home.

When a spacecraft carrying research samples from a shady corporate gene-editing experiment explodes in the atmosphere — Marley Shelton appears in this delightfully bonkers riff on “Alien,” with a giant space rat — scattering its tainted shrapnel across the U.S., George, a wolf and a crocodile are infected with the stuff. It causes them to grow to an enormous size, act out aggressively and take on the genetic qualities of other animals, like rapid cell regeneration, or exploding porcupine quills, or, you know, flying.

Hoping to save his friend, Davis links up with a disgraced genetic scientist, Kate (Naomie Harris), and barges right into the middle of the operation to take down these monsters that are threatening to level Chicago, Godzilla-style.

This is a B-movie monster flick starring quite possibly the biggest movie star (or at least the most profitable) in the world, and “Rampage” knows exactly what it is. It doesn’t try to be anything other than that. It has a decidedly 1990s feel, self-aware, quippy, loaded with archetypes.

The script smashes through rapid-fire character introductions, each bigger and broader than the last. Malin Akerman and Jake Lacy are a pair of hilarious villains, the sneeringly evil sibling corporate bigwigs. But it’s Jeffrey Dean Morgan, in fine fettle, who does as much structural damage as the monsters do, chewing the scenery as a swaggering cowboy of a government agent, replete with pearl-handled pistol on his hip. He relishes every sweet, honey-accented line delivery, but he too, is even upstaged, by the SuperCroc, who makes possibly the most memorable entrance of the year.

All these characters make for a movie that never slows down, but among all the mayhem, Johnson is completely lost. He doesn’t get a chance to truly show his comedy chops or acting skill, and his character is the least developed. He is, in fact, dwarfed by George, and every other hammy performance on screen, his presence shockingly overshadowed, his usually radioactive charisma dimmed. As a stupefyingly silly throwback monster movie, “Rampage” romps, but as a Johnson vehicle, sadly, it flops.