Greek Gods in Myth versus Literature

I have loved mythology since I was ten. There is something about the stories that captivate me. So, if there is a book or movie referencing the topic, I get excited. The more I read/watch, the more I started to notice a distinct difference between the gods in mythology and those in popular literature.

In mythology, the gods dominate over Earth, but they are selfish. They live to satisfy their own needs and desires. They collide with each other when their desires clash. They are petty and hold grudges. Their mythologies center around these topics. They are adventures, or tales of mischievous actions. Even in Homer's Iliad and Odyssey, the gods are to be feared, but ultimately like giant leaders who happen to have powers.

Literature, however, seems to focus on the darker aspects of being a god. These gods are not driven by sexual desire or personal gain. They are driven by sacrifices. Neil Gaiman's book American Gods focuses on dark characters representing gods. One basically eats a character as a sexual sacrifice. Even in the TV show Supernatural, gods are depicted as existing and interacting for sacrifices. They want people to worship them and sacrifice to them. Literature explains this is where the core of their power comes from.

What I find interesting is that, while this has religious basis, I have yet to read about it in the actually mythologies. It makes me wonder who began the trend of turning gods dark. Perhaps it has always been around. Either way, I have to say mythological gods are light and fluffy compared to literature gods. Funny because current literature is just as soft compared to the Greek classics.