Every director, actor or studio dreams of creating a film so outstanding and memorable that it deserves - nay, demands - a sequel.
Some movies are made for the sole purpose of launching into sequels, existing only to feed a franchise machine before it's next meal. Other films have follow-ups thrust upon them through shear force of will of a fanbase or the box office dollar.
However the passage of berth, movie franchises are a special thing. A unique universe of creative imagination, built from scratch for the sole purpose of our entertainment. They can take years or decades to perfect.
A successful movie franchise is incredibly difficult to construct for so many reasons. Even when done right initially, it's so easy to have them crumble in front of you if your ambition outweighs the reality, or storyline fatigue sets in.
The ending of a franchise is just as important as the beginning, it's the legacy that leaves the final taste in a viewer's mouth. A key feature of this list is, unfortunately, the result of not knowing when exactly that ought to be.
Sometimes a series will go too long. One, two or three films too many. Sometimes a remake is too tantalising for a director to pass up despite the obvious flaws and drawbacks of even attempting it.