In fairness, the movie's first hour is pretty zippy, as Sam Witwicky (charismatic Shia LaBeouf) heads East to college, leaving behind parents, girlfriend Mikaela (Megan Fox), and car (Bumblebee, an Autobot-embedded 1977 Camaro). To Decepticons carefully tracking his every move, Sam is a marked man. He's got what they want so they can destroy the sun - and humanity.
For those not current on the lore behind Transformers, which began their lives as Hasbro toys: Though Sam may look like just an everyboy, to the metal behemoths he holds the key of life. He possesses a sliver of the cosmic sparkplug that is a life force both to the benevolent Autobots and dastardly Decepticons. We are told in the prologue that the adversaries have fought on Earth since paleolithic times.
Unlike the first film, Bay's heavygoing sequel does not strike a balance between tech-loving humans and the anthropomorphic machines. It's diverting enough when envisioning a fanboy fantasyland, considerably less so when it stages World War III. (The warriors are Autobots, allied with U.S. soldiers, fighting Decepticons.)
The fantasyland moments take place in the Witwicky family kitchen where household appliances reveal themselves as pesky Decepticons; at Sam's Ivy League campus, where coeds look like Maxim Hot 100 girls; and on the open highway where sarcastic Sam and saucy Mikaela speed away in Bumblebee, with Decepticons on their tail.
(Considerably less entertaining is a sequence in which Sam has involuntary surgery, a procedure that might be called a colonoscopy of the brain.)
Roughly an hour in, Transformers 2 morphs from teen adventure into lumbering war movie. Bay and his screenwriters squander their human capital in order to show us scenes of 20-ton toys crushing 10-ton toys.
For one without an emotional stake in the Autobot Optimus Prime (voiced by Peter Cullen) or the Decepticon Megatron (Hugo Weaving), their alien blood feud has the fascination of a tempest in a steel compactor.
Periodically, LaBeouf performs one of his funny motormouth rants or Fox slinks across a scene, and the film becomes watchable.
Mostly, though, Bay busily plays one-up with other action franchises. An image of a Decepticon clinging to the Empire State Building spire looks vaguely King Kong. The design of a quick-running Decepticon is faintly Jurassic Park-ish.
Bay has a confounding sense of continuity, letting Sam leave Washington's Air and Space Museum and be surrounded by mountain ranges. Fortunately, this metal mess is enlivened by John Turturro, who shows up and injects the surprisingly raunchy film with a raunchily funny line or two.
Transformers 2 is bigger, longer and louder than its predecessor. In this case, more is less.
Contact movie critic Carrie Rickey at 215-854-5402 or email@example.com. Read her blog, "Flickgrrl," at http://www.philly.com/philly/blogs/flickgrrl.