(CNN) -- The most expensive toy commercial ever made, "Transformers," Michael Bay's live-action film about the surprisingly durable Hasbro product line, is long, loud and altogether less than meets the eye.

Optimus Prime, a good Transformer, looms over the landscape in "Transformers."

A blockbuster for 8-year-olds -- and, I guess, those older boys who never grew up -- "Transformers" will buzz its youthful demographic (the effects are incredible) but leave the rest of us wondering if Hollywood could possibly aim lower.

For the uninitiated, the Transformers are sentient machines from outer space. To pass undetected on Earth they assume the form of everyday consumer objects -- mostly, here, American trucks and cars -- but in their true configuration they are colossal robot warriors with the firepower to match.

The Autobots are the good guys, led by sanctimonious Optimus Prime. Then there are the evil Decepticons, led by Megatron, whose role is basically to blow stuff up.

Despite their name, the Decepticons show themselves first, with a devastating (and oh-so-topical) strike on a U.S. military base in Qatar. It's not the massacre of the troops that troubles the Pentagon so much as a stealth hack attack on their computer network. Could the Iranians have developed such cyber smarts? And where's "Die Hard's" John McClane when you need him?

Meanwhile, back in the U.S.A., high school geek Sam Witwicky (rising star Shia LaBeouf) is the befuddled new owner of a beaten-up yellow Camaro with a matchmaking streak. Like a certain VW love bug, the car starts and stalls at will, and likes to select golden oldies as romantic cues. It's only when Sam sees it slip away one night and transform into an Autobot named Bumblebee that he realizes this must be more than a quirky optional extra.

A filmmaker who has profitably plundered his own arrested adolescence in movies like "Bad Boys," "The Rock" and "Armageddon," director Michael Bay got his fingers burned two years ago with the relatively sophisticated sci-fi flop "The Island." It's obvious he's not going to be caught overestimating his audience twice.

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Even so, Bay is the wrong man for the job, something producer Steven Spielberg should have known. Bay's penchant for designer machismo and piledriver action (not to mention wholesale product placement) doesn't sit well with the Transformers' appropriately juvenile comedy and a sub-Spielbergian suburban teen romance. Innocence and wonder -- the type of human traits fundamental to Spielberg's vision of childhood -- are not in Bay's tool kit.

Megan Fox, for example, who plays Sam's high school crush Mikaela, looks and sounds exactly like the 20-year-old FHM babe she really is. Mind you, unless they're moms, all Bay's women look and sound this way (just ask Scarlett Johansson).

But it's military hardware that really revs his engine. Bay shoots weaponry in an orgasmic rapture, always in slow motion and against the sunset. Not surprisingly, the military was happy to play its part when it came to supplying props for what often resembles a teenage recruitment film. Even the movie's theme -- hollow words about victory through sacrifice -- is pitched to this constituency.

Setting about the action sequences with real vigor, Bay seems to imagine he's remaking "War of the Worlds," or maybe embarking on "Terminator 4." And to be fair, the Transformers in motion are something to see -- as with several of this year's event pictures, the effects guys have surpassed themselves.

But the illusion is shattered whenever the 'bots start talking or the action stops. Bay tries to gloss over the infantile plot, but it would take a lighter, wittier touch to square the movie's pedestrian script with its excitable vision of impending auto-geddon.

At least John Turturro, who shows up at the halfway mark as an unsympathetic government operative, seems to have understood that "manic" is the only appropriate response. First he's stripped to his underpants, then a monstrous machine relieves itself all over him.

After 144 minutes of "Herbie Goes to War," I knew just how he felt.

"Transformers" runs 144 minutes and is rated PG-13. E-mail to a friend

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