Monte Cook Games has Gods of the Fall as a setting for the Cypher System. In that setting, the realm of the gods fell to Earth (well, not our Earth, but still) which killed all the gods off and has caused a lot of trouble since in the form of various curses and monsters and stuff. But now, 42 years later, some beings have gotten divine sparks and are on the path to become proper gods. Of course, the process of doing so isn't easy - there are powerful people in the world who have a vested interest in the current god-less state, and there are prophecies to fulfill, and so on.
Sounds intriguing!
So it's not so much a game about being a god as it is about becoming one.
One of the frequent contributors on the SJGames GURPS forum has a long-running fantasy campaign with a similar premise. The PCs in his game started as 1000-point characters (that's the low end of potentially heroic in GURPS 4e). Now, ~400 sessions later, they're over 4000 points; the rulebook defines 500-1000 points as superhuman, so this is fairly extreme! The adventures of these new gods will be the myths of future generations. I cannot imagine, as a GM, managing to scale a single campaign across such a power range, but they're loving it.