Lucas added: "We're talking Lincoln and Red Tails (a 2012 film which Lucas executive produced) - we barely got them into theatres. You're talking about Steven Spielberg and George Lucas can't get their movie into a theatre."
Spielberg said some young filmmakers' ideas were "too fringe-y for the movies," adding: "That's the big danger, and there's eventually going to be an implosion - or a big meltdown.
"There's going to be an implosion where three or four or maybe even a half-dozen mega-budget movies are going to go crashing into the ground, and that's going to change the paradigm," he said.
Films with budgets of US$200 million (A$212 million) are increasingly common, and a number have failed in recent years, including last year's John Carter, which led to the departure of a top Disney boss.
Hollywood A-lister Will Smith's latest movie After Earth, with an estimated budget of US$130 million (A$138 million), flopped badly earlier in June, making a less-than-stellar US$27.5 million (A$29 million) on its opening weekend.
The trend towards making "edgier" films for cable TV rather than cinema was highlighted recently by Behind the Candelabra, Steven Soderbergh's biopic of flamboyant entertainer Liberace starring Michael Douglas and Matt Damon.
The film's gay theme prompted mainstream Hollywood to shy away from financing the picture. As a result, Soderbergh turned to the US cable TV giant HBO, meaning it cannot be an Oscar contender.
- AFP