John Carter and the setting on Barsoom has to be one of the coolest, unique and interesting world settings and characters out there. It has everything, from swords to science, guns to flying ships, exotic monsters, beautiful people, extraordinary action. Its really the world you want to be making movies about.
What they need is a concrete story...which interestingly enough Edgar Rice Burroughs gave them plenty of, just adapt the first book baby! It would be bad ass!