At first glance it appears to have the makings more of a low-budget sci-fi flick than of a box-office blockbuster. But Avatar, a film about a mythical planet inhabited by huge blue aliens, is set to become one of the most successful movies of all time.

In less than two weeks, the ground-breaking 3D film has grossed $745m (€520m) and is already expected to be the most successful movie of 2009-10, overtaking even the latest Harry Potter film. And on New Year's Eve it was given the presidential seal of approval when the Obama family ventured into a cinema in Hawaii to watch the movie.

Should it continue its money-making progress at its current rate, the film could become just the fifth in history to gross more than $1bn. The biggest money-spinning movie of all time is Titanic, which made $1.8bn.

Breaking the $1bn barrier would be a particularly remarkable achievement for James Cameron, Avatar's director, seeing as he also directed Titanic. He would be the first film director to gross $1bn twice.

The film's success is, according to industry experts, a payout on a substantial gamble taken by 20th Century Fox.

Despite a budget of $237m (€165m), the majority did not go on paying the wage bill – the most recognisable film star is Sigourney Weaver and others are relative unknowns. Instead, much of the money was spent developing the technology which would allow the film to be shot in 3D.

"This film really was a huge risk by 20th Century Fox," explained Charles Gant, the film editor of Heat magazine. "They took a movie that has no real stars and one with an ostensibly limited appeal. Sci-fi is typically a geeky genre so for them to make such a success out of a film that is about big blue aliens is very impressive."

The film is set on the fictional planet of Pandora, a mineral-rich world which is being plundered by humans.

It tells the story of Jake Sully, a paraplegic marine who decides to take his brother's place on a mission to the distant planet, 4.4 light years from earth. But Sully becomes engaged in battle when he learns of a plan to eliminate the planet's natives in order to mine for the precious minerals.

In its opening weekend just before Christmas, the film grossed $77m (€54m) in the USA and Canada, and an estimated €162m worldwide. When the final figures for last year are calculated, it could very well top Harry Potter and the Half-Blood Prince as the top-grossing movie released in 2009.

As well as its box-office appeal, the film has also won praise from a host of celebrities.

Before its release Ben Stiller, who currently has no films of his own to promote, went on the Tonight Show in the US apparently with the sole intention of sharing his excitement about Avatar. He told host Conan O'Brien: "I'm really excited about it. It's just going to be an amazing movie." And after seeing it, Simon Pegg wrote on his Twitter site: "The movie is a game changer. Still buzzing."

Despite only a handful of films ever achieving it, the suggestion that Avatar could break $1bn is not necessarily a fanciful one. It needs to gross another $250m but it has a number of factors on its side.

Gant added: "It has been released at a particularly clever time. Going into January and February is what is known as the awards corridor. If it wins any of the big Oscars in March, it will create the possibility that a lot of people will go to see it who otherwise would not have.

"Also, with it being in 3D, a lot of people are finding it sold out and, rather than watching it in traditional format, they are coming back to see it in 3D. It means that the film's longevity automatically increases.

"I don't think it will beat Titanic, but I'd expect it to break the magical $1bn barrier."

The biggest films of all-time

1. Titanic (1997) $1.84bn

2. The Lord of the Rings: The Return of the King (2003) $1.13bn

3. Pirates of the Caribbean: Dead Man's Chest (2006) $1.06bn

4. The Dark Knight (2008) $1bn

5. Harry Potter and the Philosopher's Stone (2001) $969m

Source: IMDB