This was meant to be the second coming of the king of comedy. Jerry Seinfeld, who in the 1990s topped the cast of probably the most successful sitcom of all time, was finally bringing another new show to American network television. Like Seinfeld, it promised to be be fresh, sarcastic, innovative, playing off the bickering and obscure disputes of everyday life.

Called The Marriage Ref, it featured Seinfeld and his celebrity pals passing judgment over the marital spats of ordinary people. It was advertised heavily and its debut was given a primetime slot on NBC, just after the closing ceremony of the Winter Olympics. And it bombed.

"The show is more Jerry Springer than Jerry Seinfeld," said Matthew Gilbert of the Boston Globe. Other descriptions ranged from "pathetic" to "painfully unfunny" via "the most God-awful mishmash", courtesy of Time magazine.

The years have not been kind to the generation of US comics that came ashore in Britain along with Seinfeld, more than a decade and a half ago. Seinfeld's other cast members were often said to be labouring under its curse in their lack of subsequent success. But the curse is also extended to many of those who worked on other hit shows.

The male cast of Friends – Matt Le Blanc, Matthew Perry and David Schwimmer – have failed to capitalise on global fame in the way many thought they would. Garry Shandling, whose groundbreaking Larry Sanders Show led the way for many other radical US imports, has almost disappeared off the public radar.

Frasier's star, Kelsey Grammer, has seen his sitcom project Hank cancelled mid-season. Even Janeane Garofalo, the actress who appeared on Seinfeld as Jerry's female equivalent, Jeannie Steinman, recently complained of the hardships of acting as she has grown older.

Garofalo, who became a poster girl for cutting edge 1990s comedy, revealed to New York magazine that she had Botox injections in an attempt to keep working. For a generation of Britons who remember their comedy heroes as confident, smart, savvy, cynical and poised to take over the entertainment world, Garofalo's comments were a depressing end point.

"Yeah, I fucking sold out," she said of having to now lose weight to obtain roles. "That is absolutely a fact. I was heavier and it really gets you almost nowhere, you realise quickly. I mean, I got very lucky in the 1990s. Very lucky."

When these shows arrived on British television in the mid 1990s, their sassy, tightly written style struck a chord with a generation brought up on The Young Ones, Not the Nine O'Clock News and Fawlty Towers. Later in the decade, these must-see shows were supplanted both in the US and in Britain by high-gloss dramas such as The West Wing and The Sopranos.

Comedy is probably the toughest road in the entertainment world. "People know if you made it in comedy, then you really do have something because it is so hard to do that," said Janette Barber, a stand-up comic and author.

Only a few made it to the top, surviving the gruelling circuits of stand-up, endless auditions then finally landing the ultimate prize: a network show. The list of comic stars who made it to the summit then stayed there is even smaller. It consists of not too many more big names than Bill Cosby, David Letterman and Jay Leno.

Far more common is the fate of many of those 1990s stars: they have a single smash hit that – unknown to them at the time – comes to represent the peak of their careers and define it forever. "To stay at the top they needed to be able to reinvent themselves as many times as possible," said Barber. But that is not easy. As Seinfeld has just found. The Marriage Ref is clearly an effort at major reinvention. It is a blend of variety show and comedy. No one is acting. Everyone is real. It is a long way from the biting yet subtle humour of Seinfeld the sitcom.

But therein lies the comic's difficulty. Typecasting is a problem for all actors and performers, but especially those who choose comedy. Sitcom stars become beloved of a mass audience who want to keep for ever performing their allotted role. No one wants them to explore new avenues. "When you try to do different characters they hate you," said Judy Carter, author of The Comedy Bible. "They want you to be that thing they loved. They don't want you to try new things."

Consider the fate of the male stars of Friends. All have struggled in their own ways despite becoming globally famous. None of LeBlanc, Perry and Schwimmer has ever really stepped out of the shadow of being Joey, Chandler and Ross. Perry's career has not taken off since the final episode of Friends in 2006. He landed a few lead roles, but they have tailed off. He has confessed to suffering from depression and fought battles with addiction. Schwimmer, after failing to become a Hollywood star, has mostly devoted his time to the theatre. LeBlanc's attempt at a spin-off sitcom from Friends was cancelled. He is now about to star in a series called Episodes in which he plays an older downtrodden version of himself in a "mockumentary"-style show about a reality TV series. One scene in the forthcoming project shows LeBlanc auditioning for the role of himself against younger, better-looking rivals.

Another problem with staying at the top is simply the temptations of fame and the fact that they have become particularly acute in a modern era of gossip websites such as TMZ and ubiquitous camera phones.

The 1990s were a different era when it came to communications. "There is more exposure and there are more chances to be stupid and make stupid mistakes," said Carter.

Look at the fate of Michael Richards, who played Kramer on Seinfeld and created one of the most singular and hilarious characters in comic television history. He struggled to escape from the shadow of his genius creation, then watched his career implode after he berated a heckler at a stand-up show and called him "a nigger". The incident, caught on a mobile phone camera, created such a huge scandal that Richards eventually had to call black civil rights leaders to apologise.

Other top stars of the 1990s have also struggled with addictions of one sort or another. The list is long and includes Garofalo and Grammer.

Finally, the industry itself has changed. The competition among TV shows in America is acute and Darwinian in the extreme. The process of commissioning a show, making a pilot, then deciding whether to axe it, has speeded up. There is almost no time for mistakes.

Even Seinfeld itself, which lasted from 1989 to 1998 and ran for 180 episodes, would never get off the ground now. Only a few initial episodes were commissioned and the audience reaction was lukewarm. The show took time to grow into a smash hit, but that is time it would no longer be given by network bosses desperate for instant success.

"Seinfeld was not a critical success at first, but NBC kept it on," said Carter. "It slowly found an audience and became a classic. But we live in a different world."

But whose version of success are we judging them on? Seinfeld's new project may have had a critical roasting but that is a long way from dubbing the man a failure. He is happily married and rich beyond the wildest dreams of many people. He has continued to do stand-up to rave reviews and huge crowds. The jabs against his new TV venture are unlikely to matter too much to him.

Others also have different priorities now. Our anxieties about their careers may reflect our culture's neuroses and expectations, not theirs. Garofalo is winning solid roles on TV shows and still working, even if she uses Botox twice a year.

Schwimmer has acted on Broadway and directed a show off Broadway. He owns homes in Los Angeles, Chicago and New York. He is a mover in politically active groups, campaigning on numerous social issues. "David Schwimmer is doing theatre. He's a social activist. He is doing what he wants to do," said Richard Dubin, a television writer and producer who is now a communications professor at Syracuse University.

Dubin is right. In judging our stars there tends to be a confusion between the role that the actor played and the desires and needs of the person behind them. Schwimmer is not Ross; Seinfeld is not even Seinfeld. The fact that many of the 1990s stars are not on TV any more, or have moved on to different roles, does not make them failures. A lot of these comic stars may not be funny now. But they are not always tragic either.

The Hit Shows

Seinfeld

Famously a "show about nothing", this hugely popular comedy was the creation of stand-up comic Jerry Seinfeld and Larry David .

Frasier

A fantastically successful spin-off from the popular long-running sitcom Cheers. Psychiatrist Dr Frasier Crane moves back to Seattle to reconnect with his ex-cop father Marty and equally self-involved younger brother Niles.

Friends

The show that came to define a generation followed the lives and loves of six impossibly beautiful, witty and usually lovelorn friends living in Manhattan.

The Larry Sanders Show

This satirical send-up of American television starred stand-up comic Garry Shandling as the self-obsessed, neurotic talk-show host Larry Sanders who interviewed real-life celebrities.