Mythology in Comics

Have you ever noticed that DC and Marvel both incorporate one type of mythology into their comics? I mean, Marvel has Thor who's a Norse god, and DC has Wonder Woman and the Amazons who are part of Greek mythology. They even have all the gods that are part of that mythology as characters! Odin, Loki, Zues, Ares! I know Marvel has Hercules who is Greek, but they don't have any Greek gods. Do you think they can copywrite a civilization's mythology?
I think there was even a Princess Diana in Greek mythology!