What Hollywood movie did take longest to create? By 'the longest' I mean full production until it made it to the theaters.
If the John Carter (2012) answer from Dr R Dizzle isn't what you are looking for this it's this:
The Thief and the Cobbler
The animated movie The Thief And The Cobbler holds the record for a movie to be in production for the longest time. It was in production stage for 31 years. (1964-1995) Then there's Love & God (1986) directed by K.Asif. He started the film in color after Mughal-E-Azam casting Guru Dutt & Nimmi. Guru Dutt died in 1964, shooting came to a halt. Then, Sanjeev Kumar was taken in the place of Dutt, but Asif himself died in 1971. The film was left incomplete. Later in 1986, Asif's wife revived the film & released it in the incomplete form. Sadly, one year before it's release, even Sanjeev Kumar died.