Wait, what?
Pirates of the Caribbean, Treasure Island, any franchise that has to do with a huge open world of pirates, real time sailing, naval battles, uncharted islands with hidden treasures, trade routes, etc...
I think a pirate game would be really good. I'm sure it was mentioned in another thread around here not long ago.
Harry Potter could be good- locations like Hogwarts, Diagon Alley, Hogsmeade, the Forbidden Forest etc.