Now this is the one I most want to see done well. Green Lantern, in any iteration, is my favorite DC Comics character. Whether it's Hal Jordan and his endless rivalry with Sinestro, or the latest duo of Simon Baz and Jessica Cruz, there are tons of great characters and stories to pull from. Imagine racing through space defending the galaxy from earth and utilizing the all-powerful Lantern Ring.
Heck, you could pull in all the other Lantern Corps and make a MMO out of it. Let the player choose their preferred color, or allow them to take a quiz to determine what they should play as, since the ring does choose the lantern after all.