If anyone still has any question as to why Dwayne Johnson is the biggest box office draw in movies today, he or she need go no farther than to watch Johnson’s latest action adventure, Rampage. With little more than his own charisma and an able assist from reliable character performers Jeffrey Dean Morgan and Malin Akerman, Johnson takes a cheesy CGI-filled tale of three, for want of a better word, rampaging monsters on the loose and transforms it from something on the level of Pacific Rim: Uprising into something that’s watchable and actually entertaining a fair amount of the time. And considering that the inspiration for the movie is a 30-year-old arcade game with fairly crude graphics in which players direct the three aforementioned monsters as they destroy various cities, Johnson’s feat is far more heroic than anything his character actually accomplishes in Rampage.

That character is Davis Okoye, a former Special Forces veteran turned primatologist at the San Diego Zoo who helps rescue and house a variety of apes. Okoye’s prize guest is George, an extremely rare albino gorilla who has become Okoye’s friend. That friendship is tested when George is accidentally exposed to a pathogen developed by medical research corporation Energyne. The company developed the pathogen to turn animals into bio-weaponized mutants so it could make a fortune by selling the pathogen to the highest bidder. Three cannisters containing the pathogen crash to Earth from Energyne’s outer space test lab, and, in addition to George, a wolf and an alligator are also exposed to the pathogen. When Energyne’s efforts to capture the infected creatures fail, its CEO, Claire Wyden (Akerman), is able to summon the mutated animals to the company’s Chicago headquarters by means of a giant supersonic homing beacon.

By the time they arrive in Chicago, the three creatures are now 30 feet tall or more and have armored plating, giant teeth and claws, and just about every dangerous attribute a screenwriter or animation artist could equip an enormous mutant monster with. Since the army and police are the usual group of incompetent bumblers one finds in movies like Rampage, the only hope to save at least parts of the city from being completely leveled is Okoye and his new helper and possible romantic interest, Dr. Kate Caldwell (Naomie Harris). She actually helped develop the pathogen under the foolishly mistaken notion that Energyne would use it to help fight cancer, but she might be able to cure the infected animals or at least stop the progress of the mutations. Also along to help is Harvey Russell (Morgan), a representative of a super-secret U.S. government agency who seems like the only even marginally competent government employee in the entire film.

While the creatures in the original arcade game were simply powerful monsters bent on leveling various cities, the movie version of George in Rampage is actually the most fully developed character in the entire film. The best CGI work in the movie isn’t the mindless mayhem that takes up the last 30 minutes of the film, but, rather, the early scenes involving Dwayne Johnson and a more normal-sized gorilla. George in these scenes isn’t on the level of Caesar in the Planet of the Apes movies, but Johnson is able to effectively bond with what is nothing more than a green screen. (Considering that virtually the entire 30-minute finale of Rampage consists exclusively Johnson performing on a blank screen later to be filled with CGI monsters, buildings, and rubble, his performance is rather noteworthy.)

Other than George, who is very effective at five feet tall and considerably less so at thirty (not surprisingly channeling every version of King Kong ever made), the rest of the CGI work is eminently forgettable. We are long past the stage where cartoonish monsters smashing downtown Chicago to bits and wiping out dozens of people in PG-13 fashion is exciting to anyone much above the age of 13. The giant wolf and, especially, the alligator seemed to have been cobbled together out of rejected drawings from various Transformers movies, and some of the interaction between the main human cast members and the monsters is jarringly fake. Director Brad Peyton has worked on several CGI-laden films in the past, including San Andreas with Dwayne Johnson, but he seems completely at a loss to craft compelling action set pieces, despite Johnson’s presence. Rampage undoubtedly is a rather expensive film, but, sadly, it doesn’t look it.

Of course, as usual in movies like this, tens of millions of dollars of CGI work are employed in service of a script that could have been crafted by a studio writing intern. Rampage appears to have been written in reverse, with the four credited screenwriters trying to figure out some pseudo-scientific means of explaining how everyone and everything winds up in Chicago at the exact same time, ready to engage in a supersized Royal Rumble. It goes without saying that the plot makes no sense scientifically and very little sense dramatically or logically. Indeed, it seems more like a SyFy Sharknado movie, except that a lot of the people involved in the film don’t seem to be in on the joke.

Fortunately, Johnson, Akerman, and Morgan are in on the joke and understand instinctively the demands on their performances. Akerman channels Paul Reiser’s performance in Aliens but her distinctly female take on the role makes it that much juicier of a scenery-stealing performance. Of course, when it comes to scenery chewing, no one is in the same league with Jeffrey Dean Morgan. He channels his rascally Negan charm from The Walking Dead but without the sinister undertones. Most actors would have played his role as a stiff bureaucrat who eventually succumbs to Dwayne Johnson’s sincerity. Here, though, he’s the smartest guy in the room, and he knows it, but he has too much fun keeping a low profile.

Having fun essentially summarizes Rampage in a nutshell. The primary actors, with the exception of poor Naomie Harris who seems lost taking her role seriously, know the exact type of movie they are dealing with and play their parts in a way as to maximize the enjoyment factor. It’s interesting that, in outward appearance, Rampage is quite similar to Pacific Rim: Uprising. Both films have giant monsters trashing a large city in service of a thoroughly ridiculous plot. But despite the presence of John Boyega, Uprising comes off far too stiff and proves a major drag. Rampage, on the other hand, will elicit its fair share of groans from knowledgeable audiences and fails to impress with its set pieces, but manages to skate by on the charm its cast and the obvious fun that its lead actors are having. During the course of a long CGI-filled summer, viewers are undoubtedly going to do much worse than Rampage on more than one occasion.