In the ten years since "Titanic" he did scrap a Mars movie and a futuristic battle movie.
"Avatar" uses 3D and other cutting edge technology in ways that tell the story, not just impress or add novelty. Cameron offered to give back points on the film to get more money for "Titanic" from FOX, but they refused saying that the film "would never make money." With "Avatar" they are counting on it making money despite the huge investment costs.
The industry is gambling on "Avatar" to get theaters and the industry to invest more in 3D projection and improved sound presentation technologies. Hollywood and its marketing wing are behind "Avatar" because it may be a way to counter the Comcast, direct to home 1080i or monitor quality rapid distribution.
Cameron can get executives to delay projects, increase money, promise promotion, and much more, despite his having trouble functioning it their Hollywood / Wall Street circles.
KCRW's the Business titled this week's episode: "The King of the World", with the following copy "James Cameron's Avatar isn't just a hugely expensive sci-fi adventure – it's a titanic bid to transform movies. We get inside the mind of one of Hollywood's biggest players with Rebecca Keegan, author of the new book The Futurist: The Life and Films of James Cameron."