Actually, you can't plagiarize something that isn't copyrighted. Greek mythology was passed down by word of mouth. How do you think they've been able to write movies like "Oh, Brother Where Art Thou?" which is based on Homer's Odyssey if this were true, or for that matter, Disney's "Hercules", the TV series "Hercules" and there's so many more. I'm pretty sure Zeus or Homer aren't going to come back from Greek Mythology and sue the creators of God of War II.