Grade: D+

There was a time when one looked forward to a new film by Guillermo del Toro with great anticipation—back when he was turning out haunting smaller pictures like “Cronos,” “The Devil’s Backbone” and “Pan’s Labyrinth,” and even “Mimic.” But with “Blade II” his priorities began to change, and he opted to make bigger, but much less interesting movies with a childish, rather than childlike, sensibility. “Pacific Rim” is the worst yet, a “Power Rangers” on steroids with an inane plot, cliché-ridden dialogue, cardboard characters and stilted acting. Roughly half the two-hour running time is devoted to city-destroying fight scenes between Transformer-like giant robots and Godzilla-ish monsters that arise from the ocean floor. That might appeal to anybody fascinated by the old Rock ‘Em, Sock ‘Em toys and the mayhem of video games, but anyone else—that is, anyone who’s progressed beyond the mentality of a twelve-year old boy—will be bored silly by it.

The premise is that earth is in the middle of a war against aliens who attack the planet not from the skies but from the sea, via some sort of wormhole through which they send gigantic monsters called kaiju. Humankind responds by building equally gigantic metal bots called jaeger, which are maneuvered in battle by two pilots whose minds are melded in something called a “drift” so that they can synchronize the movements. But after five years of combat, the earthlings are losing. The planetary leadership is on the verge of a abandoning the jaeger program—which in any event is down to a handful of robots and pilot teams—and switch to a defensive wall strategy. But the kaiju, we’re told, are getting smarter and more effective by learning from their mistakes—something that del Toro and his filmmaking crew, unhappily, do not seem to have been able to do, as their movie grows increasingly tedious as it drags on.

Thankfully the stern leader of the jaeger force, Marshal Stacker Pentecost (Idris Elba), refuses to go down quietly. He rejuvenates his dwindling pilot crew by recommissioning Raleigh (Charlie Hunnam), who abandoned the service after his co-pilot and brother Yancy (Diego Klattenhoff) was killed in combat off the Alaska coast. He’s one of the few surviving men who can pilot an old analogue jaeger that’s being taken out of mothballs to expand the few digital ones remaining, and naturally becomes an immediate subject of scorn to arrogant hotshot Chuck Hansen (Rob Kazinsky), who teams with his more reasonable father Hercules (Max Martini) in their bot. Raleigh soon sets him straight in a brawl, of course.

But Raleigh needs a new partner, and the choice is inevitable—beautiful, winsome but incredibly skilled Mako (Rinko Kikuchi), whom Stacker initially refuses to allow onto the helm of a robot for reasons that are supposed to tease us with uncertainty but are all too melodramatically obvious (and are spelled out in a series of flashbacks featuring Mana Ashida as young Mako that show del Toro at his mawkish worst—a real comedown from the mysterious ambience he brought to his early films). Stacker must eventually relent, and Raleigh and Mako become a team in more ways than one.

There’s also a frenzied subplot—supposedly providing comic relief—centered on Dr. Newton Geiszler (Charlie Day), a nerdy scientist who’s sure that gaining the knowledge to defeat the kaiju requires a mind-meld with the preserved brain of one of them, a project that takes him to Hannibal Chau (del Toro regular Ron Perlman), a dealer in kaiju body parts—much to the distress of his frazzled rival Dr. Gottlieb (Burn Gorman), who prefers developing predictive algorithms as the key to discerning the aliens’ strategy.

But all the human stuff is secondary to the battle scenes, which resemble video-game sequences without benefit of any interactivity. As bots and rubbery critters face off, innumerable bridges collapse and skyscrapers fall, though loss of human lives is merely reported on rather than shown (this is, after all, a movie that needs a PG-13 rating to survive financially). The effect will undoubtedly be thought cool by those who dote on such bloodless carnage—sort of the cinematic reversal of a neutron bomb, sparing people while annihilating structures—but after awhile it grows as boring as the final reel of “Man of Steel,” especially since the choreography and editing fail to keep the action clear and there’s little explanation for why the outcome turns out as it does in each case. The same opacity afflicts the finale, which involves an attempt to blow up the wormhole that brings a predictably triumphant conclusion, but is quite messily and murkily conveyed. (The wormhole is called the breach, so we must at least count it a blessing that the script doesn’t call for someone to shout “Once more unto the breach, dear friends!”)

Quality of acting means little in this sort of bombastic fantasy, but the cast here falls into two major groups—the solemn underplayers (Hunnam, Elba, Kikuchi, Martini) and the scenery-chewing overplayers (Day, Gorman, Kazinsky), with Perlman, as usual, pretending to be underplaying while actually going overboard with his clenched teeth. The physical production is oddly unimpressive for such a big-budget enterprise, and the same can be said of the effects, which are huge in scope but oddly blowsy in Guillermo Navarro’s 3D cinematography. Ramin Djawadi’s score goes to ear-splitting extremes in trying to juice up the action.

Perhaps it’s psychologically beneficial for del Toro to glorify the loves of his youth, but thus far the result has hardly been something others could enjoy as much as he does. His remake of “Don’t Be Afraid of the Dark” was a stinker, and this tribute to Japanese monster movies isn’t appreciably better. If you were enthralled by “Battleship” last summer, “Pacific Rim” is for you. It’s really no better than Peter Berg’s misfire, and the del Toro imprimatur doesn’t change that.