Like a defibrillator cranked up to the highest possible voltage, Rossini's William Tell Overture is slapped on to this film twice – at first briefly, then for a while. It results in something that isn't exactly a gallop, more like the protracted convulsive thrashings of a dead horse with its hoof jammed in the electric socket. Hearing the theme is always enjoyable (specifically, the Overture's fourth "Finale" movement), and maybe it's as well to reassert a wholesome association with the Lone Ranger, his horse, Silver, and his trusty guide, Tonto – and get away from the thought of Malcolm McDowell having sped-up sex with two women in Kubrick's A Clockwork Orange. But the energy, brio and brevity of that musical signature is in mighty contrast to this fantastically mediocre and long film, starring Armie Hammer as the masked Ranger himself and Johnny Depp as Tonto, produced by Jerry Bruckheimer and directed by Gore Verbinski, the men who gave us Pirates of the Caribbean.

It really is long. I have known movies by Theo Angelopoulos and quadruple albums by Wishbone Ash that seemed shorter. Verbinski has surely modified this film's running time using dastardly new temporal-distortion technology, so that each of its 149 minutes contains 250 seconds. The South American landmass peeled off from the western seaboard of Africa quicker than this.

What sort of a film is it? A family film, but too bloodless and archly self-aware to be a through-and-through western, and it's something other than an unassuming cinema version of the much-loved radio and TV adventure serials that in fact spawned two films in the 1950s. It's often self-consciously big and mythic, with Monument-Valley-grandeur tendencies that undercut the stabs at humour. Really, it's yet another superhero-origin franchise product, like the recent Superman and Dark Knight films, giving massively elaborate explanations for the hero's name and that of his horse. "The Lone Ranger" is finally spelt out haltingly, like "The Bat Man" – a legend being born. Pretty soon every film franchise in the world will be rebooted with this origin-myth style: a black-eared rodent called Michael will be tentatively hailed, at the end of a three-hour film culminating in a helium-inhalation tragedy, as "Mickey … Mouse".

Armie Hammer is John Reid, a rather mousy, intellectual fellow who arrives in Texas in the 1850s to visit his alpha-male brother, Dan (James Badge Dale), a fearless lawman who is now married to the lovely Rebecca (Ruth Wilson), for whom John still carries a torch. Dan is tracking down loathsome bandit Butch Cavendish (William Fichtner); the resulting melee brings John into contact with crooked railroad chief Latham Cole (Tom Wilkinson) and also charismatic Native American Tonto (Depp), whose people are about to be screwed over by the white man's business interests, and who finds only John is his friend. Everywhere in America, it seems, bad guys are getting away with bad stuff, and the authorities do nothing. Who can come to the rescue?

No new version of The Lone Ranger can simply leave Tonto as the lesser sidekick, and casting the A-lister Depp is perhaps intended to redress the balance all by itself. Depp brings a kind of deadpan drollery to the part, but I found his performance unbearably mannered, cute and coy. It is worryingly comparable to his catatonically detached hipster turn in the Venice-set caper The Tourist. Tonto has a wacky dead bird perched atop his head-dress, and there's a bit of comedy business here and elsewhere, but these cheeky flourishes sit uncomfortably with the need to be respectful. Depp's Tonto has a weird whiteface mask, which the actor says is based on historical photo research, but none of the other (genuine) Native Americans in the film have this, and it also looks like a way of finessing the racial imposture.

The Lone Ranger winds up looking sort of like something by Sergio Leone – though it's difficult to tell if this isn't simply a by-product of the length – and there are pale allusions to Buster Keaton and The General, but unlike Keaton, Depp gets to do his cool, deadpan stunts in the comfort of a greenscreen studio. What this resembles most of all is Jon Favreau's Cowboys & Aliens (2011) – without the Aliens – or Barry Sonnenfeld's jokey Wild Wild West (1999). Like a single-ingredient mashup, it has a smug, tongue-in-cheek pastichey feel, a passionless lack of actual interest in the imagery of the Old West, and the Lone Ranger is evoked with a fraction of the humour and zing of, say, Sheriff Woody from Toy Story. The masked man may well be back for two or three more films, but I can't help hoping that he's trotted over the horizon for the last time.