I know you’re all sick of reading about “Avatar,” so I promise to use it only to segue into something else. Don’t leave yet.

Now then. What fascinated me the most about “Avatar” didn’t have anything to do with the finished project. It was the fact that James Cameron took 12 years to make the film. (Actually longer, if you include the original treatment he wrote in 1994.) That’s longer than it took Peter Jackson to write, film and edit all three “Lord of the Rings” movies. This is an extraordinarily long time to work on one film, especially in this day and age when Hollywood often has the release dates for its blockbusters lined up before production even starts.

Cameron isn’t alone these days in bringing long-gestating projects to fruition. The Daily’s director of the year, Quentin Tarantino, had been on-and-off with his “Inglourious Basterds” for over a decade before its release, though most of that time was spent refining the script, and, unlike Cameron, he made other movies in that period as well. Together, these two Chinese Democracies of the modern film world demonstrate an inherent truth of films and, perhaps, of all works of art: No matter how good the finished product, a movie will never be as fascinating as it is in an unfinished state.

Unfinished movies take up a strange, mythical place in the world of film lore, because they’re absolutely brimming with as much untapped potential as your imagination allows. The eventual release is often a letdown, as the arrival of the actual, tangible movie can't match whatever you imagined the mysterious project could’ve been like. What sounds more exciting to you: “James Cameron’s unfinished movie promises to blow your skull off with new technology while simultaneously revolutionizing science-fiction” or “James Cameron’s just-released ‘Avatar’ is a 3-D film about blue people who worship a tree”?

And then there’s the other nice thing about unfinished movies: they’re immune to critique. I can’t develop a fully formed opinion about, for example, Terry Gilliam’s “The Man Who Killed Don Quixote,” because compounding misfortunes forced him to shut down production midway through filming. The movie was to follow Johnny Depp as he traveled back in time and joined the Man of La Mancha on his many foolhardy quests.

“The Man Who Killed Don Quixote” could’ve been Gilliam’s masterpiece. It could’ve been the definitive movie made about what has become an unfilmable subject. Or it could’ve been an utter and complete flop. There’s no way of knowing, at least not until Gilliam picks up the reins on the project again, which he is rumored to be contemplating.

There will always be a special place in my heart for films I’ll never get to see. I’m fascinated by the story of “The Thief and the Cobbler,” the intended magnum opus by Canadian animator Richard Williams (the animation director for “Who Framed Roger Rabbit”) that was in development for a record 31 years before it was wrested from his hands by Miramax and released as the bastardized “Arabian Knight” in 1995. In the case of “Cobbler,” though there is a finished project on display, it wasn’t completed as originally intended, and so it, too, will always remain in the “unfinished films” canon.

But just why is “Cobbler” so legendary? Because the scope of Williams's vision for the project was too large for him to handle, and when his dreams of meticulously hand-drawing a largely silent animated movie for adults hit the brick wall of reality, he could do nothing but throw up his hands in defeat. Williams’s dream was done in by his own ambition, and yet it was this very ambition, in all its grandiosity, that has made “Cobbler” an object of cult affection among animation historians.

Cameron had a Quixotic ambition too, but, unlike Williams, he had the good fortune of coming off directing the biggest movie of all time.