Okay, so trying to pin down a definitive 'main' list of Greek primordial gods is actually trickier than it seems, because the sources disagree and the whole concept is kind of nebulous. Most people jump straight to Gaia (Earth) and Ouranos (Sky), and Chaos gets a mention as the starting void.
But then you get into the real primordial soup with deities like Nyx (Night), Erebus (Darkness), Tartarus (the Abyss), and Eros (Procreative Love—way older than the cute winged god). Pontus (Sea) is another. Hesiod’s 'Theogony' is the go-to, but even he kinda tosses them out there without a neat ranking.
Honestly, I think the idea of 'main' is a modern imposition. They’re more like fundamental forces that just existed. The later Olympians have clearer personalities and stories, but the primordials are almost like the setting itself. You don’t really worship the stage, you know? My personal fascination is with Nyx—she was so powerful even Zeus was scared to cross her.
Anyway, a shortlist would be Chaos, Gaia, Tartarus, Eros, Nyx, Erebus, and Ouranos. After that, it gets into their kids, which blurs the line.