Obvious answer: Mogworld
Better Answers: The world needs a new mechwarrior game. Take some of the books, and make a kick ass game with that story.
OR
Dune (prequel books/original book). Imagine an action rpg where you train to be a Fremen. Maybe instead of leveling, you just learn through actions, which skills help you survive the longest. Sometimes it might be smarter to risk a run, even though a sandworm is coming your way. Or use the run as an attack, attracting a worm to eat an enemy. The spice you carry could be used like Arkham Asylum's detective vision/Crysis's visor, showing and highlighting enemies, but only a finite amount. Having to manage your water levels, while also paying attention to exhaustion (sleep), physical strain, and hunger could be fun. Hell, if you took the first wormrider (Butlerian Jihad), you have a full story, and a building of an army element, a la AC: Brotherhood. Not to mention fighting off spice farmers.
Maybe I've put to much thought into that.