The Alamo. I'm somewhat surprised there has not been a Battle of San Jacinto movie or one about the lead-up to the Civil War in Texas and how Sam Houston dealt with it.
Do the Forrest Gump sequel (based off the sequel book) and let Chet Haze play Forrest, but with the Jamaican Patois.
Cartoons are great because the characters and setting don't have to change much. Spirited away, Wall-E, Rango, Ratatouille, Princess and the frog, Night before christmas. It's tough because what makes a lot of old movies great is it being a time capsule for the people / places. The thought of most 80's / 90's movies in a modern setting with actors who are old as balls, or a completely foreign cast is gross. Goonies Superbad Django unchained No Country for Old Men 2 Talladega nights
To this day it irritates me that Master and Commander: Far Side of the World never got any sequels. It seemed set up so well. They had a LONG series of books to pull material from. It was a property that lent itself well to additional movies and more adventures. Russell Crowe and Paul Bettany had amazing chemistry on the big screen. The first was exciting, moving and hit all the right notes. I know it was expensive to make and I think the business it did at the box office maybe wasn't quite enough to justify a sequel, but to me that movie made more sense to make a sequel than soooo many other movie properties out there that get sequels. I think it is very nearly a perfect film. Anyway, my two cents.
I was going to say The Shawshank Redemption but that would probably be pretty boring as it would be just Andy and Red on the island doing their business. A more interesting one would be Eyes Wide Shut. Does Tom Cruise improve his marriage to Nicole Kidman? Does he ever find out more about the big orgy party like who was involved in it and why? There were so many questions left unanswered by that movie.