Pretend it's the 1980s again.

Pretend Margaret Thatcher is Prime Minister and Ronald Reagan is president. Pretend music still comes on vinyl and clothes still come with shoulder pads. Pretend too that there are only four television channels and you've just sat down to watch the biggest show of the decade. Here's the theme tune starting. Here's a man called JR Ewing striding towards the camera, face framed by a 10-ton Stetson. Here's the big house he lives in and here's a big car, and a pool, and a diamond necklace, and oil gushing out of the ground like it will never run out. Can you imagine that ever happening again? Can you imagine Dallas – a show about wealth and success; a show about being beautiful and rich at all costs – ever coming back? After everything that's happened? After the collapse of the banks? After all we've been though?

Strangely, that's exactly what is happening. Next week, Dallas, the show that was number one throughout the 1980s, when we still believed consumerism would make us all rich in the end, returns for a new series.

The premise is much the same – a family built from, and damaged by, money. The setting is the same – a big ranch called Southfork. Even some of the stars are the same. There's Linda Gray as Sue Ellen (greatest moment: swigging vodka from a bottle in a downtown alleyway), Patrick Duffy as Bobby (greatest moment: stepping out of the shower and revealing to his wife that the last year of her life was a dream) and, most importantly, Larry Hagman as JR Ewing (greatest moment: hundreds of them, but probably the time he was gunned down in his office and everyone asked "who shot JR?").

The good news is these original stars don't just do cameos in the new series – they are right in the thick of the action – although they are joined by new, younger actors too. There's JR's son John Ross, played by Josh Henderson, Bobby's adopted son Christopher, played by Jesse Metcalfe (who starred as John Rowland in Desperate Housewives), and Bobby's new wife Ann, played by Brenda Strong. They are new Ewings who walk on the old fault lines of money and greed and sibling rivalry, and it's this that provides much of the plot for the first episode as John Ross and Christopher clash. John Ross's DNA is 95% JR so he thinks drilling for oil on Southfork is a good idea; Christopher is Bobby's son and the new moral compass in a family whose direction is usually towards money – he thinks alternative fuel is the future.

The fact that this struggle is at the centre of the first episode shows that the new head writer and show-runner, Cynthia Cidre, understands what needs to stay the same in this show, and what needs to change. The 1980s was a decade when we got bigger and became more successful – we sailed on oil – but this new version of Dallas is coming back post-crash, post-Bush and even, arguably, post-American dream. America, and the world, is a more angsty, worried, less confident place, and so Dallas has to be too.

The symbol of all of this is JR himself. When we last saw him at the end of the 1980s, he was still as cocky as ever, drillin', cheatin' and connivin', but our first glimpse of him in the new series is a shock. He's now in his 80s, he lives in a care home and he hasn't talked for months because of depression. Bobby, who has just been diagnosed with cancer, visits him and bemoans the past. "I'm sick of this family tearing itself apart over money," he says. JR says nothing. It's the economic meltdown symbolised by two men, but, of course, it can't stay like this. We need to know that JR has been punished but we also need JR to rise again, and that's the shameful, exciting secret of the success of this show: sometimes we like the bad guys to win.

When JR does finally emerge from this malaise, jolted out of it by Bobby's plans to sell Southfork, it's wonderful to see the electricity crackling in Larry Hagman again. Hagman was always the best thing about Dallas – it was why he could command pretty much any salary he wanted – and, even though the show became silly in its later years, he always had good scriptwriters prepared to have a bit of fun. At the heart of this was his relationship with his vodka-swilling wife Sue Ellen: they clung together and ripped each other apart at the same time. "What slut are you sleeping with tonight?" asked Sue Ellen in one episode. "Whichever one it is," says JR, " it's got to be more interesting than the slut I'm looking at now."

There's more of this kind of stuff in the reboot, this time with JR's new enemy, Bobby's wife Ann. "In my wildest imagination," she says to him at one point, "I never dreamed you would stoop to this." "Well," says JR, "you're just gonna have to work on your imagination."

None of this soap-opera confrontation is real of course: JR is a character that's been heightened, that's had all the brightness and volume turned up to maximum, but what he isn't – even though some people think this is what Dallas is all about – is camp. Dynasty was the camp show because it was aware of what it was; Dallas wasn't because it was the first of its kind, creating drama out of those early days of the 1980s; it was the shows that followed, self-consciously trying to do what Dallas did, that made the genre seem camp.

As head writer of the new show, Cidre seems to get this. "This is not Dynasty, no slur on Dynasty, but this is not a show where people pull each other's hair out, falling in fountains," she has said. "The caveat on that is that this is Dallas and we want to have fun. We want to love to hate the bad guys, have some flair. The situations are slightly pumped up as it's melodrama and it's a soap but we're grounding it in real human behaviour."

It is probably this that will make Dallas work again, even if some viewers feel it's out of place or vulgar in the new post-recession world. For a start, Cidre has cleared out some of its wilder excesses – no-one will be stepping from showers and telling us we've all been dreaming, at least not yet – but she's spotted what Dallas, underneath all the 1980s bling, was really about: sibling rivalry and the fact that, in most families, brothers secretly, and sometimes openly, hate each other. Hagman recently put it this way: "Everybody has a jerk like this in their family, a father or brother or uncle or cousin. That's what makes JR so appealing to people. They know who he is." And if you think there isn't a jerk in your family, then it's you.

And even if this wasn't true, even in this new, recession-hit world, there is something to learn from JR. In the 1980s, he was rich and successful; he was something we all wanted to be. But in this new world, he is something we must avoid becoming, and a warning too that JRs are still out there. In one of the old episodes, JR explained this by laying out his rules for life, all with a big Texan smile on his face. "Don't forgive and don't forget," he said, "And do unto others before they do unto you." But Hagman put it better himself when he made an important, slightly scary point about his most famous character. "I don't think I was an evil man, I was just a businessman. I'm just doing what people do for business."

And maybe in the end there's another, sadder lesson we can learn from the story of JR Ewing – a lesson about television and how it has changed. In the 1980s, 21 million British viewers saw the Who Shot JR? episode (in case you need reminding, it was Sue Ellen's sister Kristin, played by Bing Crosby's daughter Mary). But those were the days when there were four channels; this new version of Dallas is back in an age when, as Linda Gray puts it, there are nine million channels and cable and the computer to compete with. It means those old channels simply do not have the reach they once had, and that means audiences are no longer as united as they once. If JR ever gets shot again, there aren't that many people who will see it, or even care.

The new season of Dallas begins on Channel 5 on September 5 at 9pm.