A big ape prepares to do battle with his gorilla friend.

“Rampage” is one of the better video-game-based movies, a low bar that it clears only by forsaking the entire premise of the game. The mid-80s arcade hit had one objective: with a giant gorilla, giant lizard, or giant wolf as your avatar, you destroy every building and eat every civilian you can get your hands or claws on. The movie, of course, makes it about stopping the monsters from wrecking and devouring, because we have to pretend that seeing buildings crushed and people killed isn’t why we watch movies like this.

Anyway, as movies about giant animals wrecking cities go, this one is passable if you can ignore most of the humans and all of the dialogue not spoken by Jeffrey Dean Morgan (we’ll get to him later). Our protagonist is San Diego Wildlife Sanctuary primatologist Davis Okoye (Dwayne Johnson), who has a special relationship with George, a normal-sized albino gorilla fluent in sign language (including obscene gestures) and fond of practical jokes. (The movie treats George’s supernatural intelligence as normal.) We’re told that Davis is a misanthrope who prefers animals over people, but this assertion is undercut by Johnson’s refusal (or inability) to turn off his charisma. For someone who hates people, Davis is very personable.

George is infected by an experimental pathogen accidentally released by the tech company Energyne, run by venal billionaire siblings Claire (Malin Akerman) and Brett Wyden (Jake Lacy). These over-the-top villains created “weaponized DNA” (to what end I don’t know) that makes its host grow in size, strength, and aggression. Also infected were a wolf in Wyoming and an alligator in the Gulf Coast, both developing cool mutations that George didn’t get. Poor George only got larger and angrier, then broke out of his enclosure to go on a spree — a “rampage,” if you will. Davis’s team is contacted by Dr. Kate Caldwell (Naomie Harris), the fired Energyne geneticist who developed the pathogen, who says she may know how to cure it. Once she arrives, everyone on Davis’s team besides Davis is forgotten for the rest of the movie.

Enter Jeffrey Dean Morgan as Harvey Russell, a philosopher cowboy who works for one of the government’s more secretive organizations. (“When science s***s the bed, I’m the guy they call to change the sheets,” he says.) He believes what Davis and Kate tell him, unlike the military, which wants to just drop bombs on Chicago (where the monsters are converging) until the monsters are dead. But if Davis can calm George down, maybe George can help pacify or kill the other two and Chicago can live to be destroyed another day.

The movie is directed by Brad Peyton with the same casual disregard for life and property he brought to “San Andreas,” in which California was wrecked by an earthquake but the only people who mattered were Dwayne Johnson and his immediate family. Peyton’s singular devotion to Johnson continues here. When Harvey Russell is trying to get the military not to bomb downtown Chicago because there are still un-evacuated civilians there, the satellite footage that convinces them doesn’t show the women, children, and first-responders caught in the rubble; it just shows Davis Okoye. If you want to survive, you need to stick close to him.

Apart from Morgan’s colorfully folksy government agent, none of the humans are interesting. The brother-sister villains (evidently inspired by certain Trumps) are cartoonishly amusing but disappear early. (Also vanishing before we’re ready to see him go: Joe Manganiello as a scarred mercenary hired by the Wydens to capture the mutant wolf.) The screenplay, credited to Ryan Engle (“The Commuter,” “Non-Stop”) and three other men, is consistently jokey — not funny, per se, just not serious. These movies CAN be clever and humorous in addition to having spectacularly convincing special effects (which this does), but it takes extra effort. “Rampage” prefers the path of least resistance: mindless banter interspersed with skyscrapers being knocked over.

Crooked Marquee

C+ (1 hr., 55 min.; PG-13, moderate profanity, a lot of destruction violence, a little gore.)