This is based on the backstory of Sonic.exe as told by its creator. Basically Sonic.exe is a demon that created itself and toys with its victims but rarely kills them. When it does kill them, it eats their souls. It thinks itself superior to any Gods or demons on Earth. The game Sonic.exe is how it manifests, because as it isn't of this world, it can't exist in it.
Hopefully I got that right, I was going from memory.
Another Sonic.exe pic from me