spoilers for stargate and egs
also maybe star trek at the end
The immortals in EGS are the same general thing as the Ancients/Ori (ascended beings) in Stargate. It is just that they have different self-imposed limitations and exist in different places.
Part 1
In the main EGS universe, the immortals have the law that they can only empower and guide people, and that they should reset (wipe most of their memories) every so often.
In an alternate EGS universe, these beings are called ancients (iirc) and have a different law thingy. Might reset, idk.
In the main Stargate universe, the Ancients have a similar empower/guide/non-interference rule, but do not have the reset thing.
If the immortals do the memory-wiping, but the Ancients don't, that could be why most of the Ancients are really not feeling mentally up to any task, and why they don't do anything about anything. They've "seen so much in so many places, so many heartaches, so many faces," and they're just depressed.
Part 2
also iirc at least a couple of the Ancients were Greek or Roman gods, the "builders of the roads". it was SG-1 season 2, like The Fifth Race or something
There's an immortal who calls himself Zeus after resetting, presumably every time he resets. It is possible that, long ago, he called himself Zeus and was the real Zeus until he named himself not to be Zeus anymore.
Part 3
In EGS, all magic users are descended from immortals. In Stargate as well, it seems like the magic user (Adria) is a child of the Ori and the human Vala.
Part 4
There's also something up with the Q from Star Trek. Both the Ancients (SG-1 season 7 or 8 finale?) and the Q (in Voyager) have brought humans to a corporeal representation of their reality. DeLancie Q had a child with magic powers, although I'm not sure that we've seen a Q have a child with a human.