User blog comment:Twilight Despair 5/Oldest Enemy or Species./@comment-24766308-20120516141607/@comment-3045936-20120516165520

The superwiki gives on http://www.supernaturalwiki.com/index.php?title=Mythological_Arc_Timeline

Distant Past
At some point in the distant past, God, Death and other deities come into existence.

God creates the Leviathans, but grows concerned that they will try to destroy His other creations. He creates the realm of Purgatory to contain them, and seals the Leviathans away.

God then creates celestial beings including Archangels, Angels and Cupids all of which will dwell in Heaven with Him creating an angelic society collectively known as The Host of Heaven.

God instructs the angels that they should bow down to humanity, but Lucifer refuses because he sees humanity as flawed and unworthy. Eve begins creating the Alphas of the Supernatural beings, and is eventually imprisoned in Purgatory.
 * Lucifer entreats his brother Michael to support him but he refuses
 * God instructs Michael to cast Lucifer out of Heaven
 * Gabriel tires of the family arguments and leaves heaven, hiding on Earth disguised as a Trickster
 * In definace of God, Lucifer takes humans, strips them of their humanity and creates demons. The first of these is Lilith.
 * God then imprisoned Lucifer with Six-Hundred Seals, sixty six of which have to be broken for Lucifer to escape his confinement

I think after God and Death the pagans came to be. But seeing as they aren't in anyway related to his creations God doesn't like them. What I mean is, like Demons once being human soul, Leviathans being one of God's work, and monsters with souls minus the Alphas are just turned humans. The pagan gods just appeared they weren't created by God directly, or a mutated or twist version of one of his other creations, like demons and monsters.