I really love Greek mythology (more than Norse) as well as the Star Wars, Lovecraft, Tolkien, and Stephen King mythoi respectively. I'm starting to look more into the mythologies and folklore of various cultures all over the world and throughout history. I've also taken an interest in the William Blake mythos among other things.
Not really the same thing, but if you like fucked up sci fi, check out The Culture novels by Iain M Banks. Absolutely huge works of imagination. Indescribable really.
I'm mentioning it because it's similar to the fiction you described in that it's like a whole other universe with its own history and everything. Not sure if you could really say it's a mythos but it's not far off.
I love my Greek Mythology. On the Modern side, the Marvel world (Avengers, X-Men, Spiderman, etc) is incredibly interesting as well as Stephen King's Roland Deschain material. As soon as I finish the 8 dark tower books and the Little Sisters or Eluria short story I am going to try to get my hands on the graphic novels.
If you're into that stuff check out The Power Of Myth series by Joseph Campbell. There's a book too but I haven't read it. The series I'm talking about was broadcasted back in the late 80's. He goes and breaks down why myths came to be, why they are and how they relate to us today. It's really fascinating and interesting stuff.
CS Lewis has done some cool ones too. The space trilogy is my favorite (as well as one of my favorite series of all time). It combines lots of druidic/arthurian and christian themes in the overall history of the solar system.
I took a greek mythology course in university. We read Hesiod, homer, Sophocles, etc.. What I got from most work was "bitchez be crazy" and the most glorious things in life were killing and raping.
I found it fascinating that the entire reason Achilles was pissed off was because Agamemnon stole his captured sex slave. When Achilles told Agamemnon to "enjoy her to the hilt" i literally laughed out loud. 2800 years ago and people were talking about going balls deep.
You know what has always bothered me about the Iliad? Diomedes never gets his do in modern mythological awareness. Most people can name a handful of warriors from the story, Achilles, Hector, Odysseus, Ajax, Paris, Patroclus if they saw Troy, and Agamemnon, but now one remembers Diomedes who was probably the second best fighter in the whole war behind only Achilles. Hell he beat Hector twice and Aeneas, wounded Ares and Athena (matching only Hercules in wounding gods).
Hector's brother said this about him, "He fights with fury and fills men's souls with panic. I hold him mightiest of them all; we did not fear even their great champion Achilles, son of an immortal though he be, as we do this man: his rage is beyond all bounds, and there is none can vie with him in prowess."
Is Diomedes that other half-god fellow who just went about wrecking everyone in his path?
I do remember someone who gave Ares what Homer referred to as a minor flesh-wound or something, which had him running away like a pansy. I found it hilarious.
It's been quite a while since I read The Iliad and I got lost in all the names. But, ya, The Iliad really does show how humanity hasn't changed one bit in the thousands of years.
I loved Greek mythology when I was a child. Nowadays I haven't followed much mythology, but I do like the fictional worlds Stephen King created. Lovecraft would also be included if he actually bothered to develop it beyond "There are unimaginable alien races, and then unimaginable god-like beings, and then beings EVEN more unimaginable than them and... oh! oh! Guess what? There's some MORE beings even more unimaginable than them!!!@#!"