Which Hollywood movie is the greatest waste of potential?

I know a lot of critics' mantra is "Hollywood sucks." I don't think so. When I see a disappointing Hollywood movie, I think "If this & this were different, it would be great..." I think there are people and companies in Hollywood with passion and great ideas, but so much gets lost dealing with other people and companies.

What is you greatest "Could have been" movie?

And if you wish, speculate on where it went wrong.