I won't be seeing the movie version of Les Misérables until next weekend, but I'm really looking forward to it. I'm curious as to whether it lives up to the stage version, which is likely to get a box-office fillip. In his review, Guardian film critic Peter Bradshaw has shown that it's possible to be impressed by both The Master and Les Mis – but perhaps it's no surprise that some commentators have taken the opportunity to give the entire artform a good kicking.

In a deliberately provocative piece, the Evening Standard's David Sexton remarked that he and many others found the idea of people acting, singing and dancing at the same time repellent, and denounced musicals as "an innately idiotic form" which is embarrassing and stupid. He went on to say: "It isn't that we don't like drama or don't like music. Indeed, it may well be because we value them both so highly that we loathe them both being travestied."

It's probably true that a bad musical (take your pick from The Man Behind the Iron Mask, Menopause: The Musical or Peter Pan El Musical ) is harder to endure than a bad play, but that's only because there's so much more to get right (and which can go wrong). Bad musicals are uniquely memorable, which is why it's easy to compile a musical hall of shame.

But these things are complicated. Plays more often get a chance to be re-staged and reassessed – David Hare's The Judas Kiss was greeted coolly on its premiere in 1998, but has been pronounced a success in a revival with Rupert Everett – but with the exception of Sondheim, musical flops are seldom revisited (although it was reported last week that Cameron Mackintosh has plans for Moby Dick, a show which bombed back in 1992). In recent years, small venues such as the Union and the Landor have done an invaluable service for musical theatre with their chamber revivals of shows not seen for years. They have also provided opportunities for the increasing numbers of highly skilled performers graduating from musical theatre courses such as Laine and Arts Educational.

Yet the sheer passion of some musical-lovers for their chosen art form can be a little discombobulating to those who don't know their Mame from their Hello Dolly! In his blog for the Stage last week, Mark Shenton posed a quiz asking asking Are You a Genuine Musical Theatre Nerd? – a quiz I'd probably fail, along with many theatre critics. Theatre criticism – largely because most critics come from a literary tradition – has always been short of critics who are really knowledgeable about the form, which may in part explain why musical theatre occupies such a fragile place in theatre culture.

For my money West Side Story is as great achievement as its source, Romeo and Juliet, and My Fair Lady every bit as good as Shaw's Pygmalion. You would have to be terminally high-minded to fail to squeeze an ounce of joy from Guys and Dolls or Matilda. Popular doesn't always mean pap – and a form which brings such pleasure and joy to so many deserves to be celebrated and treated to the same informed critical scrutiny as the latest play by Tom Stoppard.