I heard somewhere that "I am God" is a difficulty setting on a video game, maybe a first-person shooter like "Duke Nuke'm" or "Wolfenstein". Correct. God is also a very common name for video and online game players. Also the name of the sniper in the Navy Seals movie.
For another "domestic" explanation of the note, see my post #117.
#146 by Shooter2.5 is more detailed and accurate about the game setting.