3. Tron: Legacy (2010) - 28 Years
Tron is a unique film all on its own. In 1982 when the original Tron was released, it was pushing a boundary unlike anything before it in special effects. It was not allowed to be nominated for an Oscar at the time due to computer FXs being considered cheating. Although Tron from 1982 may look cheesy now, it is still a farfetched ride that was never seen before. Tron: Legacy picks up with his son 28 years later finding his way into a dictatorship led Grid full of oppression of computer programs.
Was it worth it? I'm going to "why not?" What made Tron so popular was the level of special effects it attempted, it only seemed proper if a good story was presented to see how it would fair in a modern world full of limitless computer generated effects. Some may argue that parts of the story were weak but I would never say that is enough to call it a worthless sequel. 28 years is a long time but Tron: Legacy found a way to write a story that didn't seem forced but natural without going out and insulting the audience or legacy of the original. It was enjoyable and a lot better than what could be expected of a film with such a long gap in-between films.