You often hear superheroes referred to as "new gods".
In fact, during a period after he co-created the Marvel Universe, Jack Kirby went to DC and created a group called the New Gods.
I knew for my upcoming ICONS campaign setting, the USHER Dossiers, I would be treating the "old gods" as supers (not that original) but I decided to lay down some ground rules to give it an earthier and more realistic spin.
First, I thought it would be awesome to go WAY back.
The first metahuman in the USHER campaign was born in 70,000 BCE and he still walks the Earth today. At least, everyone assumes he does. He hasn't been seen in over 10 years.
Second, I have fully embraced the "1 in a million" concept- well, actually, I embraced it about 20 years ago when Roger Moore first created it in an article he wrote for the Marvel-phile in Dragon magazine, but it's on full display here, going all the way through the setting.
I used some world population statistics to give a guideline on the number of metahumans alive at any given point in human history, one per 1 million population.
Of course, no one has hard data on world populations that far back, but I picked an estimate and treated it as gospel.
So if I want to set the Titanomachy (the war between the Titans and the classical Greek Gods) in 4000 BCE, that gives me a total of 7 metahumans to work with worldwide.
So there ended up being a grand total of 4 metahmans involved in that fracas, preventing me from doing the obvious (and imo less interesting) thing of taking every single titan and every single greek god and making them supers.
I will say though, that I have noticed the Law of Conservation of Ninjutsu in effect for my burgeoning ancient-supers history.
For those who aren't familiar with this seminal storytelling device, it basically says that there's only so much Ninjutsu to go around. So if one ninja shows up, he's amazingly deadly, whereas if 100 ninjas show up, they're cannon fodder and you cut through three of them with one sword swing.
In other words, the heroes and villains around when there were only 5 total metahumans tend to be AMAZINGLY powerful.
Ok, done rambling, time to write my version of the Aesir-Vanir War.