Superman Returns (12A) <!-- none onestar threestar fourstar fivestar -->

Is it a bird? Is it a plane? No, it's that strapping Boy Scout who wears his underpants - a sober shade of burgundy nowadays - over his blue bodysuit: the worst superhero outfit in the known universe. Please remind me how this guy managed to escape being a laughing stock. More pressingly, how has Clark Kent managed to last so long without people identifying him as Superman's alter ego? Batman and Spider-Man have their masks. The Hulk has his green skin and grotesque musculature. Superman has... simply removed Clark's spectacles and, hey presto, he's unrecognisable! I've heard of hiding in plain sight, but this is ridiculous.

Superman has returned to bring mankind what his father called "the light to show the way", though it's plainly not enough to show them what's in front of their face. The old man (a hologram Marlon Brando from the 1978 movie) adds, "I have sent them you, my only son," a phrase that reminded me of Michael Murphy arguing with Woody Allen in Manhattan: "You think you're God!" "Well, I gotta model myself after somebody." This isn't just a saviour descended to Earth, this is a second coming. It transpires that he's been away for five years visiting his native planet, Krypton, now a dismal wasteland.

In the interim some things have stayed reassuringly the same - for instance the Kansas farmstead of his adoptive mother (Eva Marie Saint) and the sleek Art Deco lines of Metropolis - while others have (as they say) moved on. Arriving as Clark Kent at his old desk-job on the Daily Planet, he finds that his beloved Lois Lane (Kate Bosworth) is not only a Pulitzer Prize-winner, she's also the mother of a five-year-old boy and is now engaged to the paper's hot-shot assistant editor Richard (James Marsden).

She won the Pulitzer, by the way, for an article entitled "Why The World Doesn't Need Superman", which would be hurtful on a professional level but feels even more pointed given their history together. Say it isn't so, Lo! Rather than play the jilted lover, however, Superman responds to the slight by saving Lois and other terrified passengers aboard a jet that was plummeting to its doom. He succeeds in bringing the plane to a gentle halt on the field of a packed baseball stadium, then reintroduces himself to Lois with an, "Are you OK?" That he accomplishes this rescue act in a quite unassuming manner is down to Brandon Routh's nicely judged restraint in the title role - not for him the triumphant smirk or the one-line quip as he performs his wonders. This superhero is young, but not brattish; he can lift megaton weights, but doesn't show off his muscles; he's driven by duty, but doesn't bemoan his lot. In short, he proves that humility is one of the finer parts of being heroic.

If only they had fitted that heroism around a better movie. The plane-saving feat turns out to be the highlight of an increasingly frenetic sequence of set-pieces, mostly concerned with the geological mischief wrought by his old adversary Lex Luthor (Kevin Spacey). Thanks to a load of crystals he nicked from Superman's glacier-bound hideout, Luthor has created a new landmass that has blacked out the whole of the Eastern coast of the US. Now he wants to supplant the continent altogether.

"Millions of people will die," says Lois. "Billions!" he crows back at her, though one look at his new continent - a jagged mass of barren rock - makes you wonder if his plans for global domination are slightly off. Spacey plays it camper than Liberace (is that the reason for the grand piano on his yacht?) and wears the duds to match, including a chocolate-brown corduroy suit alarmingly similar to one I own: I had no idea this was the preferred attire of the modern megalomaniac. Parker Posey plays his sidekick, though on what grounds she was recruited remains a mystery. She asks dumb questions, has no special gifts or tricks, and evinces no romantic or physical interest in Lex. Is she his beard?

It's not that you actually mind watching this stuff. It's as polished and professional in its way as last week's Pirates of the Caribbean sequel, and director Bryan Singer has the sense not to dawdle: like his X-Men movies this keeps a brisk tempo. Nevertheless it demands a shade over two and a half hours of your time, and for no discernible reason.

There aren't any cliffhangers worth the name, and the longed-for reconciliation between Superman and Lois is handled too coyly for anyone to notice. Kate Bosworth's 1940s look is right for the retro stylings of the production design, and her different-coloured eyes (one brown, one blue) offer the teasing hint that, like Superman, she's not entirely of this world either. Unfortunately she hasn't a very light touch, and makes Lois more of a petulant miss than perhaps was intended. I ultimately found myself hankering for Margot Kidder in the 1978 movie.

So Superman has returned, and the box-office will stuff its giant maw with cash for another few weeks. Two cheers for Brandon Routh and his revitalising of the role, though you will search in vain for any new angle on the square-jawed hero from DC Comics. The bangs are longer and louder, and Routh is rather daintier on his feet than superheroes tend to be. But his airborne mission to mankind doesn't inspire wonder, even in this unheroic age.