Better known for his uncannily life-like impersonation of the former Prime Minister in the 2006 film The Queen, than for his roles in Blood Diamond and Laws Of Attraction, the boyish 39-year-old actor is still trying to break free from Downing Street.
He's managed an escape of sorts in new film Frost/Nixon, where he plays another British institution, Sir David Frost.
The film began as a play by Peter Morgan and has already been a hit with stage critics, but will British film audiences admire his portrayal of the much-loved television journalist as much as they adored his Tony Blair?
In Frost/Nixon, David Frost is presented as a failing 70s TV personality, desperate to boost his flagging career. In a bid to make his name, he buys the first-ever television interview with disgraced ex-president Richard Nixon after the Watergate scandal.
Hoping to force an admission of guilt from Nixon and make broadcasting history, Frost takes on the ferocious former president who has other ideas.
Michael says the reaction to the play on London, Broadway and finally on screen, has been extraordinary.
"I talked with people who've seen the play, and the movie, and they say they get to a certain point and realise they haven't breathed for a minute. Any story that makes anybody that engaged, well it's a good sign. We were surprised when we started doing the play that people were on tenterhooks about it. Especially when most people know the outcome."
The Welsh actor's knack for disappearing under the skins of famous men (he played Oscar's lover in Wilde and Kenneth Williams in Fantabulosa) assured him a safe acting passage to Hollywood.
But despite recent roles in Blood Diamond, alongside Leonardo DiCaprio, and Laws of Attraction, starring Pierce Brosnan and Julianne Moore, Michael still hasn't managed to eclipse the fame of his 'real life' characters. Frost/Nixon may change that.
Watching his attempts to catch out the former president (Frank Langella), like a precocious puppy taunting a tiger, is utterly compelling. Critics say his performance as the tanned, egotistical Frost could win him an Oscar, with the movie already up for five Golden Globe awards.
"I felt like every time we did the performance, and then the film, whenever we were together there was always something real going on. It was never a repeat of what had been done before," he says.
"But as specific as the story is about this series of events, I think there's also a lot of universal stuff in it."
Michael knows he was fortunate to be cast as Frost. Director Ron Howard (A Beautiful Mind and Apollo 13) chose him ahead of established names like Kevin Bacon, Oliver Platt and Sam Rockwell even though he'd never played a Hollywood lead.
Michael, the son of a part-time Jack Nicholson lookalike, says the hardest part of moving the play from stage to film was keeping it real.
"The challenge was to play someone who has, on the surface, a superficiality and lightweightness, but to try and get across how much things are unravelling underneath.
"On film, I just had to trust that the inner life would get picked up by the camera. Whereas on stage you do a certain amount of projection, more broad strokes."
Michael was still a student when he first appeared in a West End production, starring opposite Vanessa Redgrave in 'When She Danced'.
The sprite-like Welshman went on to receive three Laurence Olivier Award stage nominations in four years, before beginning a film career.
But the former boyfriend of Kate Beckinsale, with whom he has a daughter, says that growing up in the small town of Port Talbot (also home to Richard Burton and Anthony Hopkins), was the thing that most helped him find the Frost role.
"David Frost came from very humble beginnings and the idea of feeling slightly out of your depth is something that's very strong in this film.
"Frost always felt slightly on the outside and that his background was holding him back in some way, in the eyes of other people. That's something I experienced in having come from Talbot and going to drama school in London. Going to the big city and having that feeling of 'Am I going to be accepted?'
Luckily, the well-respected TV presenter has been gracious about the play, and the film. But Michael says that playing a person who is still alive can be complicated.
"I kind of avoided meeting Sir David until after we opened on stage because it's a fairly warts and all portrayal, and he's such an engaging, nice man. The danger was that I might avoid going into certain areas because I felt we already had an established relationship."
Under strict orders to stay away from the notable television personality, Michael admits he accidentally bumped into him mid-way through rehearsals.
"I'd been sworn off going to see him by writer, Peter Morgan, and then I saw him walking down the street one day. I have to admit that I was his stalker and followed him around. I watched how he walked and all that sort of stuff, and took pictures of him on my mobile phone. To this day he's not even aware of that!"
But does he ever get tired of mimicking real life?
"I've done a lot of those characters and I do really enjoy it," he says.
"But playing real people is sort of like a tightrope walk. On the one hand, the character exists as the character in this script.
"But the more research you do, the more you start to feel protective towards the real person. I find myself saying to the director, 'Maybe we could put this in', and suddenly you realise it's not a character study - it's a story. So it's a balance between responsibility towards the story and responsibility towards the real person."
MICHAEL SHEEN - EXTRA TIME
:: Michael has a nine-year-old daughter, Lily, with former girlfriend Kate Beckinsale. Kate left Michael for director Len Wiseman when they met on the set of Underworld, a fantasy film in which Michael played a werewolf.
:: Michael is soon to appear in another film written by Frost/Nixon and The Queen scriptwriter Peter Morgan.
This time he'll be playing Brian Clough, the famed footballer turned manager, who once said: "I wouldn't say I'm the best manager in the business, but I'm in the top one."
:: Not many actors have played former Prime Minister Tony Blair twice; once in the Channel 4 drama The Deal in 2003 and again in the film The Queen, starring Helen Mirren, in 2006.
:: Although Michael missed out on the sequel of the film Underworld, reports are that he'll be back for the third instalment.
:: In an interview, writer Peter Morgan, stated that even if he wrote a film about Britney Spears, Michael would be able to play the lead.
:: Frost/Nixon is released nationwide on January 23.