They watch so you don't have to. But which shows do TV critics admit to overlooking – and which reviews do they stand by?

What is the point of TV critics? It's a question which has been asked countless times: sometimes in anger, sometimes in despair, sometimes out of genuine interest. Are they there to educate, inform and enlighten? To help posit a general case as to whether something is good or not based on their own personal views? Or are they there simply to be funny and amuse their audience?

A A Gill thinks he knows. "The purpose of the TV critic," the Sunday Times's man in front of the box solemnly told this year's Sheffield documentary festival, "Is to sell newspapers." Gill says he writes for his readers, even though he admits he is not quite sure who they are. He doesn't really rate his fellow critics (Ally Ross of the Sun excepted) and believes most have been put in their jobs by editors "who don't know what to do with them except to have a colour writer of some sort".

But are TV critics prepared to admit when they got something wrong? Or have they ever got something unbelievably right when the rest of the world was too bovine or glass-eyed to see it? "I know you all love it, and I'm willing to accept that not loving it is my loss," Gill wrote in 2008 when forcing himself to revisit Little Britain USA (even though he seemed to hate the later episodes even more). For him, there is an inherent unfairness in reviewing just a first episode of a television series. "Sometimes a series can get better so I do go back and say something is much better if it is. I feel that's proper and I don't feel diminished by it," he told me.

So we asked five of the nation's other leading TV reviewers and writers to 'fess up to their biggest mistakes – and the moments they thought they got it right. What did they have to say?

Andrew Billen (TV critic, The Times)

Biggest mistake: State of Play

When I was TV critic for the New Statesman I wrote an excoriating review of the BBC's State of Play's first episode, only to discover the rest of the nation loved it. The next week the star letter was an excoriating review of my review, including, most humiliatingly, a critique of my analogy of the cheesy thriller's plot to an Edam. Apparently it does not have holes in it. The writer won a pen or book token or something. I thought at the time, why don't they just sack me the old-fashioned way. I still don't think State of Play was all that special but it became a Hollywood film, so what do I know?

Usually, however, I tend to give new things the benefit of the doubt – recently Silks and Monroe – and then discover they are really rather ordinary and the best writing has gone into the first episode. The safe thing is to give everything three stars out of five but where is the fun in that?

Jaci Stephen (Soap columnist The Daily Mail, former TV critic, Mail on Sunday)

Biggest Mistake: The Office

When I watched the first episode off The Office, I was not sure whether it was genius or plain boring. I went with the latter, deciding that as I had seen so many bizarre and excruciating things in newspaper offices, I couldn't see the point of simply replicating events in a far more tedious place. I still prefer Ricky Gervais's follow-up, Extras, but have to acknowledge that The Office is a masterpiece. I didn't get the chance to revise my opinion in print because the Mail on Sunday dropped the TV review page. That's offices for you.

I think I was right to praise the EastEnders baby swap story, even though it seemed the whole nation was up in arms about it. The quality of the acting – Jessie Wallace, in particular – pulled it off.

Sam Wollaston (TV critic, The Guardian)

Biggest mistake: Battlestar Galactica (probably)

Well, I was lukewarm about Rev when it started, and it went on to win awards. And I was even less enthusiastic about the IT Crowd. But you know what, I stand by both of them. Rev was nice, but in a very gentle way – it didn't really do anything that the Vicar of Dibley didn't, it was hardly groundbreaking. I did do a bit of a U-turn on that one though. The IT Crowd is also just an old-fashioned sitcom, the humour based on misunderstandings and falling into traps. So I'm not U-turning on that. It's lame.

There are few shows I just haven't got, or just don't understand the humour – such as Psychoville, but then I never got The League of Gentleman either. And then there's Battlestar Galactica, which I can see deals with people and humanity, but I have an inbuilt prejudice against – I'm a science-fictionist ...

Harry Venning (TV critic, The Stage)

Biggest mistake: Our Friends in the North

I remember putting the boot into Our Friends in the North, which then turned out to be something of a classic and a personal favourite of mine. Throughout episode one I was so focused on the heroic, but ultimately futile, attempt to transform the adult into teenagers that I failed to spot the production's many other qualities. Daniel Craig, I remember, offered a particular challenge to the makeup department.

Other regrets include pouring unrestrained scorn upon sitcom writers, whose ranks I've since joined. I always thought My Family was consistently funny and well written, while every other reviewer used it as a benchmark for all things bad about sitcom. But since it was pretty much critic proof anyway our opinions were totally superfluous. In fact, they usually are superfluous. Especially mine, which are printed after the programmes have been broadcast, by which time everybody has made up their minds anyway.

Gareth Mclean (Radio Times' writer-at-large and former TV critic, The Guardian)

Biggest Mistake : The Lost Prince (BBC2) and The Death of Klinghoffer (Channel 4)

My guiding principle in being a critic is: what do I think? And, erm, that's it, really. Everyone thought Bonekickers was terrible, and I gave that a kick-in, but everyone but me liked Gavin and Stacey. I haven't changed my opinion on Gavin and Stacey, it's just a show that a lot of people really loved but I didn't. I'm not an idiot because I didn't like The Wire. It just didn't engage me.

You get into trouble when you write what you don't think. The times I have done that – second-guessing other people and/or questioning myself – are the reviews I regret. In 2003, I thought Channel 4's version The Death of Klinghoffer was dreary but thought I should like it and so described as not really my thing. I was subsequently skewered by David Herman in Prospect . (This is not me complaining about getting a bad review, by the way). The same thing happened with Stephen Poliakoff's The Lost Prince. I watched it, thought it was plush rubbish but with everyone else raving about it, equivocated and ended up praising it.