Oliver Stone's historical epic Alexander opened in the US on Wednesday to a savage reception from critics.
Colin Farrell plays Alexander the Great in the film
The New York Times said the film, starring Colin Farrell, had "puerile writing, confused plotting and shockingly off-note performances".
The Los Angeles Times called it an "indifferent epic" that was merely a vanity project from director Stone.
But novelist Gore Vidal has defended it, saying it was "barrier-breaking" for its frank depiction of bisexuality.
With a reported budget of $150m (£79m), Alexander charts the life of Macedonian leader Alexander the Great, played by Farrell.
The portrayal of Alexander as bisexual and having a relationship with childhood friend and battle commander Hephaistion, played by Jared Leto, has stirred controversy and the threat of legal action from Greek lawyers.
But Vidal praised the film for tackling bisexuality, which he said was taboo on screen in Hollywood.
It was "a breakthrough in what you can make films about", he said.
"Movies are always the last to register changes in society and this movie does it."
Most reviewers were less generous, saying the battle scenes and historical reconstructions were the film's best points.
The Los Angeles Times critic wrote: "There's nothing fresh about this plodding endeavour, nowhere it goes that other films have not gone before."
Angelina Jolie plays Alexander's mother Olympias
The New York Times said it was "dry and academic where Troy was vulgar and wilfully ahistorical".
Trade paper Variety said: "Startling visions of antiquity, the likes of which have never before been put on the screen, will surely stay in the mind long after the dramatic vicissitudes have been forgotten."
"But much of the nearly three-hour running time is devoted to knotty personal and geopolitical issues that most viewers won't give a hoot about," critic Todd McCarthy wrote.
And Rolling Stone magazine asked: "How's Alexander? Not great.
"Though the battles have the blood-and-sinew bravado you expect from Oliver Stone, this three-hour buttnumbathon is hamstrung by a hectoring grandiosity."