Music biopics: For those about to rock, please don't bother

It's so brilliant you wonder why nobody thought of it earlier. Sacha Baron Cohen, the mankini-sporting star of Borat, is to play Queen's Freddie Mercury. There, I thought to myself, is a film I'd like to see. But then I pondered a little more about the picture that might be made, a rags-to-riches story starting in Zanzibar and concluding in a Kensington mansion, a tale of a man who battled with his sexuality and his fame. There will be drugs, there will be fornication, there will be jumpsuits aplenty. Who, you wonder, will play Brian May's hair?

Despite its propensity for ludicrousness, the rock biopic has never been more popular. Lately we've seen Kristen Stewart and Dakota Fanning as The Runaways, Sam Riley as Joy Division's Ian Curtis and Andy Serkis as Ian Dury. Now there are countless more in the pipeline: Al Pacino as Phil Spector, Amy Adams as Janis Joplin and David Morrissey as Julian Cope. Rumours abound online of Robert Pattinson playing Kurt Cobain, Mike Myers as Keith Moon and Outkast's Andre 3000 as Jimi Hendrix. Clearly, if film studios are to be believed, we can't get enough of rock'n'rollers on screen.

And why not? The lives of rock stars are ready-made dramas complete with outré outfits, sex, drugs, paranoia and, in many cases, death. The chapters within these fictionalised accounts are already laid out: the troubled childhood, the struggle for recognition, the epochal concerts, the premature death bringing with it the mouth-watering taste of immortality.

So why are the results so consistently abominable? When rock stars get the Hollywood treatment, more often than not the films emerge as tawdry soap operas, earnest snooze-fests or unintentional comedies that end up echoing one of the few good (alas, fictional) rock films ever made: This Is Spinal Tap.

There have, of course, been a scattering of decent ones, among them Walk the Line, What's Love Got to Do with It and Alex Cox's Sid and Nancy. All of these played fast and loose with the facts and yet offered, largely through the ferocity of the central performances, convincing portraits of musicians struggling with their personal lives and the weight of professional expectation. More recently, Anton Corbijn's Control captured the look and the mood of Joy Division even if it shed more light on Ian Curtis's domestic arrangements than his inner genius.

But these are the exceptions to the rule. Most heinous of all is that mainstream rock biopics invariably lack the crucial insight into the creative brilliance that turned the musician in question into a living deity. Instead they wheel out the same stereotypes – would-be icons surrounded by Machiavellian managers, baffled band-mates, sinister drug dealers, ornamental groupies – amid tired tales of ambition, egotism, self-abuse and redemption.

Then there are the bad outfits and the slippery accents that frequently make the rock flick more about impersonation than performance. If it's pantomime you're after, look no further than the Jerry Lee Lewis biopic Great Balls of Fire! starring Dennis Quaid, a film so zany that it merited an exclamation mark in the title.

When the actors struggle, it's often left to the wigs to take centre stage, their presence so powerful in certain films that the viewer cannot think about anything else. Remember Michael Pitt's blonde curtain as Kurt Cobain in Last Days? Or Leo Gregory's plumped-up bowl cut as Brian Jones in Stoned? And how about Meg Ryan's mousey fright-wig in Oliver Stone's 1991 film The Doors?

The Doors signifies all that is laughable about the rock biopic, an example of how to take a serviceable rock'n'roll story and, through blinkered adoration and unforgivable pomposity, render it both ridiculous and boring.

The moral of the story? Leave the films to the film-makers and the music to the musicians. And, for the love of God, leave poor Freddie alone.