I go through phases with my reading, and I'll be honest and say that I thought of the following idea in 2010 when I was immersed in a comic book/graphic novel phase.
A fascist US government imprisons all super heroes/villains and forces them to kill each other in gladiator-style combat. Society goes along with it.
So, this could work as a story within one of the existing comic book houses with known characters, or it could be something entirely new.
The Alan Moore/Watchmen influence is obvious, but rather than explore the downfall of the super beings, I thought it'd be interesting to explore what happens to our heroes when it's society that fails them. How do they respond? How do we?