Hero or villain, clever or clueless, war leader or war criminal, it's hard not to have an opinion on President George W Bush.

During eight years in office, he's been the butt of a slew of jokes, with his legendary mispronunciations and Texan drawl. His decision to go to war with Iraq, reaction to Hurricane Katrina, and his leadership of a country in mourning after 9/11 have made him one of the most talked-about presidents in recent history.

Not one to shy away from controversial subject matter, director Oliver Stone has attempted to put a human face on the much-maligned leader of the free world in his new film W, handing actor Josh Brolin the arduous task of playing the president.

"When Oliver first approached me, I thought, why would you want to do a movie about that, when you can watch this guy on CNN? I had a very cosmetic view of Bush, and Oliver," 40-year-old Brolin admits.

"Oliver has a very controversial reputation, which I found out later is superficial. So my perception about him – and, as it turned out, about the movie, was totally wrong. But initially I said no. I told him I would love to work with him, but I just had no interest in going there. And the fact that Oliver was even seeing any kind of connection between me and Bush was slightly insulting. Oliver, instead of being put off by that, was intrigued. He said 'just read it'. So finally, I did. I was taken aback, moved by it – impassioned and saddened. And above all, I identified with it. I asked my son if he would read it because I respect his opinion a lot. He did, and his response was, 'You cannot NOT do this'. After reading it, I'm thinking, this is the greatest job an actor could ever have."

Somewhat of a veteran at making presidential biopics, with films such as JFK and Nixon to his name, Oliver Stone's W is the first-ever movie about a sitting US president. Perhaps unsurprisingly, Bush declined to be a technical adviser on the film.

"Usually when you do a biopic, you cover about 10 years of a life, but here, you go from 21 to 58," says Brolin.

"I was thinking, 'Can I live up to it?' I just spring-boarded from a lot of fear. I think it was based on fear of pulling it off."

Certainly, the movie sees Bush go through a multitude of changes – from his youthful days as a hard-drinking party animal to his conversion to Christianity, newfound sobriety and decision to run for president. His later years, as covered in the film, follow his administration's discussions over the war on terror. But it was Bush's early life that intrigued Brolin the most.

"We played with the idea of, well, what was he like in his hometown of Midland, Texas?" he says.

"Did he do all that stuff as a young man? Was all the stuttering and breathiness caused by tension? Did it increase in office? How much is too much? This is our version of George W Bush and his life. It's worth doing, especially considering the impact he has had on the world."

Brolin is joined in the film by a strong ensemble cast that includes Elizabeth Banks as wife Laura, Thandie Newton as Condoleezza Rice, Richard Dreyfuss as Dick Cheney and James Cromwell as George Bush Sr.

"I was a big admirer of James Cromwell; he's so regal looking and such an amazing actor," says Brolin.

"I'd never met him, but I thought he'd be perfect for the role and so did Oliver."

Stone says "Josh gives the great performance of his life" in the film and early reviews in the US have added to the plaudits for the actor.

But it wasn't easy for Brolin to give Bush a human face without turning him into an object of fun. "The thing about this president is he
is an exaggeration of himself, even he admits that," Brolin says.

"It's fun to watch. What we've tried to do is create a drama with the realities of those exaggerations but not making it into buffoonery. I don't think we did. They've done that themselves, but
we haven't."

Then there are the comic touches in the film. Bush's mispronunciation of words, the infamous pretzel choking incident and his constant eating – all moments which Brolin says adds colour and depth to the final cut.

"To get the impact of drama in two hours, you need comedy to take a breath, in order to ingest what's being said in the movie," he says.

"That was what was important to me. Bush is an exaggerated personality. There are gestures of his that you can't deny and are hilarious. That's why there's so much cartoonish impersonation of him. So when you're doing the movie, you're searching for the tones and you don't know what it is. And what we've come up with is a very dramatic version, with comedic overtones."

Playing Bush is the latest in a string of recent roles which have formed part of a career resurgence for the actor, who is married to actress Diane Lane – he has two children Trevor, 20, and Eden, 15, by his first wife.

After a promising start as a teen actor in Steven Spielberg film The Goonies, he starred in a number of flops before landing roles in Quentin Tarantino's Grindhouse, In the Valley Of Elah and American Gangster.

Last year's starring role in Oscar-winning film No Country For Old Men cemented Brolin's reputation. After W, he appears in new Sean Penn movie Milk.

"I'm very happy with what I've been doing – working on great movies with great directors," he says.

"I don't want to do Iron Man. I don't want to do The Incredible Hulk. I'm just not interested. My value is going up. Look, man, I've always been very happy. I've been given the fortunate gift to be able to make money in this industry. That's huge. Now I feel I can relax a little bit. All I ever wanted was choice. Suddenly I have
this choice."

But Bush will stay with Brolin for a long time yet.

"Ultimately, it was the most fulfilling role I have ever done," he says. "Because it was absolutely the biggest challenge."