Age. The Elder Host of my campaign didn't create the world, they were called into it from Nothing. In their passage across the world, celestials, fiends, elementals, and all the other outsiders and elementals came into being where the shadows of the Elder Host fell. There was a typical rebellion, the oldest of the gods was slain, and giants, dragons, gnomes, and humans were created from his body (bunch of evil races created from his head, too, but that's a different thread).
The Elder Host had "relations" for various reasons with the mortal races, and the children of these affairs became the Dalerain.
The Elder Host are the oldest and most powerful; they hold the broadest and most important portfolios (life, death, elements, change, entropy, knowledge, ignorance....). The oldest Dalerain are next on the hierarchy of power, though not all of them have seemingly very important portfolios (the god of smiths, being the firstborn Dalerain, can kick hinny on the god of all the oceans and seas in the world, 'cause he's older).
Generally the youngest are the Envidier, quasi-divine heros. Envidier are alot like saints; they are well-known and honored, but not actual deities.
There are Ascended, non-divine mortals who somehow acquired a portfolio. The god of trade and commerce, once a mortal, managed to convince (or trick) the Dalerain god of trade and commerce into selling his portfolio to him (that Dalerain is now an Envidier placated by those seeking to avoid a bad or foolish bargain).
Cheers
Nell.