Autobot Optimus Prime prepares to battle the Decepticons in Transformers: Revenge of the Fallen. (Jaimie Trueblood/Paramount Pictures)

As Isaac Asimov might have observed, a robot without a personality is just so much fancy metal. That was the big drawback to Michael Bay's first Transformers movie — C-3PO had more character in one of his gold-plated fingertips than all 13 of the protean robots in Bay's 2007 blockbuster. If you weren't a fan of the original 1980's toy/cartoon, you found yourself confusing one giant shape-changing machine with another – and the director's Cuisinart editing style didn't help matters.

The robots are the major improvement; otherwise, director Michael Bay sticks to the formula that made his first Transformers feature a box-office smash.

Transformers: Revenge of the Fallen, the sequel, more than makes up for that. Finally, we have robots we can root for (or hiss at), not just a bunch of sentient scrap heaps slugging it out. The standouts are Bumblebee (voiced by Mark Ryan), the comically moody Autobot, who poses as a yellow and black Camaro and communicates via his radio; Wheelie (Tom Kenny), a whiny, bug-eyed little Decepticon hiding as a remote-control toy; and slapstick twins Mudflap (Reno Wilson) and Skids (Kenny again), a couple of trash-talking bots from the 'hood. My favourite, though, is Jetfire: a creaky old codger with a British accent (Ryan again) and a steel beard that jangles like wind chimes, he's taken the shape of a warplane in one of the Smithsonian museums.

The robots are the major improvement here; otherwise, Bay sticks to the formula that made his first Transformers feature a box-office smash. He just makes everything bigger, though not always for the better. He ratchets up the wacky comedy, but also lays on so many drum-rolling sequences of the U.S. military in action that the movie begins to look like a recruitment ad. He goes on location to real wonders of the world – the pyramids of Egypt, Petra in Jordan – but then spends an interminable amount of time pretending to deface them or blow them up. (The running time is 150 minutes and, by the end, it sure feels like it.)

The first Transformers ended with the unlikely hero, everyteen Sam Witwicky (Shia LaBeouf), helping the good Autobots from the dying planet Cybertron defeat their evil enemies, the Decepticons. The sequel finds the Autobots living peacefully among humans in their guises as various motor vehicles, while secretly helping the American army hunt down stray Decepticons – who can assume any form, from a fighter jet to a cellphone.

Sam, meanwhile, is off to college, reluctantly leaving behind his Autobot guardian/first car, Bumblebee, and his smokin'-hot girlfriend, Mikaela (Megan Fox, working hard to bring the belly shirt back into fashion). However, when the Decepticons return to Earth seeking a thingee called the Matrix – the key to a machine that can suck all the energy out of the sun – Sam & Co. are drawn back into another alien-robot showdown.

The college setting allows writers Ehren Kruger, Roberto Orci and Alex Kurtzman to switch from fanboys to frat boys – there's a steady run of dick jokes. It also brings out Bay's past experience as a commercial director, with Sam ending up at a campus party that looks like one of those sleazy Budweiser spots. (Judging from the hot-chick quotient, he's enrolled at Playboy U.)

LaBeouf, a budding comedian stuck in the action genre, is at his best in these early scenes. Especially when his wisecracking Sam is playing off his Fred-and-Wilma parents (Kevin Dunn and Julie White) or his new comic foil, hyper roommate Leo (Ramon Rodriguez), an enterprising conspiracy theorist who winds up as Sam's sidekick.

Mikaela Banes (Megan Fox, left) and Sam Witwicky (Shia LaBeouf) are caught in a clash between alien robots in Transformers: Revenge of the Fallen. (Jaimie Trueblood/Paramount Pictures)

The funny stuff also gives us a chance to appreciate the stone-cold Fox. True, she's mainly here to serve as wet-dream fodder for the picture's predominantly male demographic — we first see her in tight jean cutoffs, provocatively straddling a motorcycle like something out of a Maxim photo spread. But she brings a saucy edge to Sam's spunky trailer-park dreamgirl. And, after she blithely dissed this movie in a recent EW interview, you have to love her even more.

By the midway point, LaBeouf, Fox and Rodriguez have been demoted to mere action figures, ducking, rolling and making hair's-breadth escapes from Decepticon villains. Among them: the blade-wielding Scalpel, tongue-lashing Alice (Isabel Lucas as a robotic snake hiding inside a curvaceous co-ed) and their master, a dude called The Fallen (hence the movie's title).

It's up to John Turturro to restore the levity, reprising his role as Simmons, the obsessive government agent in charge of tracking extraterrestrials. Simmons has been lying low, working in his mama's deli, but the new robot crisis brings him out of retirement. Thank heavens for that. Wearing strange underwear and spouting patriotic slogans, a gleeful Turturro proceeds to steal every scene he's in.

In the end, though, all must surrender to Bay's master plan — that is, to once again pack in as much violence per film frame as physically possible. The big battle scene in Egypt has so many explosions and shots of characters fleeing in slo-mo that Bay seems to be creating a primer for cheesy action-movie clichés. (The icing on the cake is composer Steve Jablonsky's laughably ponderous Gotterdammerung-style score, complete with heavenly choirs.)

At least the Transformer clashes are more entertaining this time out, thanks to Industrial Light & Magic. The FX company has made the robot features stronger and more distinctive, so we can tell who's slamming whom. In the first movie, you felt like you were staring with bewilderment into the jumbled contents of a Meccano set.

Now that the robots are better, the next thing the Transformers franchise needs to fix is the pacing. Bay builds the first part of this film skillfully, but after that he just jams his foot to the floorboard and the rest of it roars by at a relentless, numbing speed. Maybe he's afraid that if he gives us time to think, we might realize just how absurd this whole enterprise is: a $200-million spectacle based on a child's toy.

Transformers: Revenge of the Fallen opens June 24.

Martin Morrow writes about the arts for CBCNews.ca.