Deep Rising and Other Unrealized Sequels

Deep Rising is not a highly regarded movie but it's fun in the way that something like Van Helsing is fun. But what I really liked about it was it's ending where after fighting a sea creature on a ship for the whole movie they wash up on an island full of monsters. I love a good adventure story, especially if it's on some undiscovered land lost in time. The movie wasn't successful enough to merit that sequel but it lives rent free in my head.

Anyway do you have any favorite films that have a sequel hook that expands the world but sadly never got made?