Powergame is a free, fast superhero RPG system that has been in development on and off for over 20 years. http://www.kotiposti.net/~trmika/powergame/
The game was originally a parody of sorts, based on the Marvel Super Heroes Game From TSR. Several editions later, it has become more serious in tone.
There is a fan created setting, which was born out of fluff from earlier editions of the game. It's pretty extensive.http://powergame.tripod.com
I have seen this game mentioned a few times on the RPGNet forums. Seems to be one of those well-kept secrets that only gaming hipsters know about. Welp, time to wax those mustaches, boys, we're part of the cool kids' club now!
Lastly, here is a review from RPGNet:https://index.rpg.net/display-entry.phtml?mainid=4469