"It's interesting as one hand, there's something of Trump about the man," says the actor, who plays the leading role in the film, The Founder, which examines the beginnings of the fast food empire as a simple Californian drive-in. Parks and Recreation actor Nick Offerman and John Carroll Lynch play the brothers.
"The difference is Donald Trump may have worked hard but he certainly had the enormous advantage of being born wealthy, whereas Ray Kroc was not. But Ray is less than ethical at the end of the movie, and I suppose I could say that in certain ways Donald Trump appears unethical," Keaton continues.
"Ray Kroc also became this larger than life character at the high point of his wealth, and Trump is unbelievably needy to the point where it's funny - but it's also frightening."
The Founder is also "a movie about America and a movie about capitalism", according to its director, The Blind Side's John Lee Hancock.
"It was definitely about capitalism rather than fast food - the rush to make more."
It's also about what might have been, unwittingly, modern capitalism's first major corporate takeover. Ray Kroc was a 50-something travelling salesman when he met the McDonald brothers, two businessmen who lost their money in the Depression of the 1930s, but who had built up their own California roadside restaurant.
Struck by the fast service, high-quality food, disposable packaging and the family atmosphere, Kroc asks to start franchising the brand, although the brothers are happily committed to their original restaurant and its small workforce.
Eventually, Kroc bought the McDonalds name, the company and even built a branch of McDonalds opposite the brothers' original restaurant, putting them out of business.
Despite a handshake agreement that the McDonald family was to receive 1 percent of all future profits from the chain, it never occurred. Last year, the company made US $1.31 billion (Â£1.0 billion) in profits and had stores in 118 countries.
"I think it's an interesting take on what the American Dream has become to those watching from outside - that even a million isn't enough," Keaton says.  "That it's not enough to lead a good, comfortable life - that you need a billion dollars to have 'made it'. Ray Kroc basically mechanised capitalism - he wanted a billion dollars.
"I always thought that the American Dream, in its simpler form, was 'work hard, have a house, go on vacation.' That's what it was, but it's no longer the perception of it.
"Ray Kroc did actually say 'if your competitor is drowning, stick a hose in his mouth.' Now I'm a fan of hard work, there wasn't a time in his life that my Dad didn't have two jobs. I'm not a fan of sadistic greed, but as an actor it's intriguing."
As the first 'fast food' chain, McDonalds has gone on to have far-reaching impact, "and not only in the way we eat," Keaton argues.
"It's changed culture beyond food. It basically became the Henry Ford mechanical production line for food, but it's helped build a portable society, a disposable society, and that's not overblowing it.
"Part of the year I live on a ranch, and I'm not even talking about the effect of too many cattle producing methane, it's about overgrazing of the land to produce so much meat. People just don't realise how that affects the environment."
Keaton points out that another hot topic crops up in the film - that of immigration.
"Kroc pursued the McDonalds name because he thought it was so American - even though of course, it's Scottish," he says. "His own name was Slavic and he thought of it as less. But it's a reminder that the whole country's an immigrant - I grew up in Pittsburgh in the 50s and it was full of Russians, Poles, Irish and Italians. Trump's an immigrant, basically."
However, the 65-year-old actor says he does admire certain things about Kroc. After early success in 1988's Beetlejuice, and playing Batman in 1989, Keaton's career has kickstarted again in his 60s with roles in recent Oscar winners, Birdman and Spotlight.
"I admire Kroc's perseverance, hard work, focus and will," he says. "And the guy was 52 when he began this journey, and in those days, that was old. I admire all of that, I just don't admire what came later - the masochistic greed.
"It can't have been all about the money, it must have been about power. He stole the whole thing about being 'the founder'. Or possibly maybe he was able to justify it. Maybe he said to himself, 'I am the founder of what this became.' That's a pretty good argument- that the McDonald brothers had a nice idea about serving burgers, but he went so much further."
The Founder is released in the UK on 17 February
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Michael Keaton's new role is, he thinks, "a Trumpian character," as he takes on the part of Ray Kroc, the 1950s salesman who wrested the McDonalds name from the restaurant founders, Dick and Mac McDonald, and turned it into a modern day global franchise.