With a beneficent wave of his hand, George Lucas declines to make a fuss. It is his 58th birthday and he's in a joyless hotel suite talking about work, but hey, he says with a shrug, that's the way it goes. The checked shirt and scraggly beard are his regular-guy camouflage. He talks in an affable drone. The billionaire creator of Star Wars is anticipating the premiere of Attack of the Clones with the unshakable good humour of a man who controls everything he sees. "I'm sure this one will do fine," he says, reclining contentedly.

If there is a tinge of defensiveness in his sunny tone, it is because the latest instalment of Star Wars will inevitably be hammered for failing to live up to its 20-year-old predecessors. Such was the fate of The Phantom Menace and, although this is a better film, it will be received by many Star Wars purists as laughable. There is one scene in which Anakin Skywalker thrashes camply about in his sleep, crying "No!" at his nightmares. It is such a terrible cliche that one assumes it was put in for parodic value; it certainly had the audience in hysterics when I saw it. Lucas doesn't smile. "It's not deliberately camp. I made the film in a 1930s style. It's based on a Saturday matinee serial from the 1930s, so the acting style is very 30s, very theatrical, very old-fashioned. Method acting came in in the 1950s and is very predominant today. I prefer to use the old style. People take it different ways, depending on their sophistication."

This hangs in the air for a few moments. The universe that Lucas created for Star Wars is vastly sophisticated, but the characters are for the most part folksy vehicles for the delivery of quaint moral lessons. This is key to the films' charm - the marriage of futuristic landscapes with old-fashioned values. It renders the dialogue starchy and ludicrous, and there seems no other way to receive it. Harrison Ford famously turned to Lucas after reading his Star Wars part and said, "George, you can type this shit, but you sure can't say it."

Lucas says he never claimed to be good at writing dialogue. "I've always been a follower of silent movies. I see film as a visual medium with a musical accompaniment, and dialogue is a raft that goes on with it. I create films that way - very visually - and the dialogue's not what's important. I'm one of those people who says, yes, cinema died when they invented sound. The talking-head era of movies is interesting and good, but I'd just like to go to the purer form.

"The problem is, the theatre aspect of it has sort of taken over, and the institutions that comment on film are very literary. They aren't cinematic; you don't have a lot of cinematic people talking about cinema, because visual people don't use words, they use pictures."

We seem to have swung round to blaming the unsophisticated critic again. There is a pause. "There's a little difficulty there, which I understand," he says indulgently, although his tone suggests that for "little difficulty" you should read "pig ignorance". "Cinema has only been around of 100 years or so - not long enough for people to really understand it."

In the hierarchy of people who understand film, Lucas naturally places himself at the top and meddling executives at the bottom. The impetus for making the first Star Wars films, he says, was in part to grow rich enough to buy his independence from the studios. He suffered at their hands over the making of his first film success, American Graffiti, which was almost never given a cinema release. It wound up making $120m, having cost $750,000 to make. Lucas learned a lot from that - most importantly to trust his own instincts.

"I'm stubborn and creative. Anybody who works in an artistic medium trying to create something does not like people looking over their shoulder going, 'No no no, make it blue! Make it green!' If you have a vision, you don't want a lot of outside influence. A director makes 100 decisions an hour. Students ask me how you know how to make the right decision, and I say to them, 'If you don't know how to make the right decision, you're not a director.' That's all there is to it. If you have to think about it, you can't direct something. There are directors out there who don't know how to make up their minds, but a true director has an idea in his head and can instantly weigh any decision against that and say, 'That's right, that's wrong.' You welcome feedback from talented people, not marketing people or executives who aren't creative."

After the success of the first Star Wars trilogy and the breakdown of his marriage to Marcia Griffin, Lucas retired to Skywalker Ranch in California and devoted himself to raising his adopted children, Amanda, 21, Katie, 13, and Jett, nine. Lucas himself grew up in a modest home in the American midwest, where his father owned a stationery shop and taught his son the value of good business sense. He tries not to spoil his own children, and the remoteness of the ranch offers some protection against their turning into Hollywood brats.

"I live a reasonably simple life, off the beaten track," he says. "Occasionally they'll come to a premiere and obviously I have friends who are famous, but they just know them as friends. My son doesn't know that Steven Spielberg is a big-time movie director - he just knows him as Steve. Its not until they get to 12 or 13 that it occurs to them who these people are. Like with Hayden Christensen(the actor who plays Anakin Skywalker), my daughter was around when we hired him and said, 'I like this one better than that one - he's cuter.' Now suddenly he's famous, where before he was just this actor coming in looking for a job."

He is a dad before being a director, he says; workaholism and parenthood don't mix. "I get up, I work out, I get my kids up, I take 'em to school and then I get to work at 8.30 or 9am. I always quit at six and I don't work weekends. I take my kids on set with me and we hang out as a family. One of the reasons I stopped directing was that I knew I couldn't really live a lifestyle like that and raise family. Before I had kids I was a workaholic. I was obsessed. Now movies are my second priority in life. If it doesn't get done today, it'll get done tomorrow.

"I'm independent, so I don't have crazy people saying they'll fire me if I don't come in to work on a certain day. I worked very hard to be able to be in a position to say, 'I'm sorry, I'm going home to have dinner with my kids now.' "

Lucas has grown up since he made the first Star Wars, but he wrote the story for the current trilogy when he was still in his 20s. He hopes that his youthful exuberance is preserved in it. In the 1970s he never imagined that the technology would exist for him to be able to film the back-story - he believed that at best it could be written as a book.

In his head, Lucas sees the nine films as a whole. He can't wait for the next generation of children to watch them in the right sequence. He gets enormously animated about it. "It'll be a very different experience, because when Darth Vader walks into that spaceship with the princess, they're going to think, 'Oh my God, that's Anakin!' and they're gonna see Luke and think, 'Oh my God, that's his son!' And rather than a surprise when he says, 'I am your father,' it'll be like, 'Oh my God, finally he's told him!"

I ask if the children will notice the disparity in special effects between the first and the middle three episodes. "I really don't think so, because it's about telling a story, not about special effects. The first series was written very carefully around the technology of the time and it pushed the effects as far as they could take it. That's why it all takes place on Death Stars, in the outreaches of the galaxy, in areas where there isn't much stuff going on. And the back-story was never written to be made into a movie because technically you couldn't do it - to get Yoda to actually have a swordfight would be impossible. I mean, I could barely get him to walk."

Lucas thought long and hard before returning to Star Wars. This would be a 10-year commitment. And whenever he saw a movie he liked, he thought how tedious it would be to be locked into doing Star Wars rather than following his fancy. "Even something like Black Hawk Down, I thought, 'Oh man, I want to make a movie like that.' "

In the end, though, it simply came down to the story. After 20 years in his head, he wanted to see it on screen. "And I was hoping," he says, with a sudden gust of little-girl modesty, "that everyone else would want to see it too."

· Star Wars II: Attack of the Clones is released on May 16.