Has this type of plot been done before? Is it interesing?

This story is about a devil that is banished from the demon world and sent to earth. Subsequently, there is a war on earth that rages between humans( who are cyborgs with advanced weaponry) and flesh eating humans who are possessed. So basically its a big role and he was banished for committing a sin and the only way he can retrieve his honor and place is by killing of the human race and taking over it. However, there is also the fact that he is "good" and makes good friends with the humans. So he has to make a choice between fighting for his human friends and alliances or getting his throne back.