Well first of all, when we're talking about Norse mythology we need to be very careful with giving a certain answer as to what that mythology actually was. The danger there lies a lot with the fact that just about every single scrap of information we know about how these religions practiced were written down by christian scholars hundreds of years after there was any actual pagan presence there.

So a very real danger is that a lot of what we have on Norse mythology is actually that a lot of these stories that scholars like Snorre Sturlason wrote are 'warped' in the eyes, probably unwittingly, of his christian mindset. The idea of there being an "underworld" (Hel) and heaven (Valhal) is what many scholars argue is typical of a Christian archetype that's been interjected into the stories whereas what precious little we have of manuscripts and source-material that Snorre used doesn't explicitly say anything about this.

As for greek mythology, it's just as important to note that this is something that we have found multiple sources on throughout quite a wide space of time and they've changed considerably depending on the source material. The first variant we know of is the Pelasgian creation myth before the Greek Dark Ages around 1200 BCE which Homer's Iliad refers to. Interestingly, it speaks of a female serpent-like goddess, Eurynome, who created the elements and caught the north wind, making it the serpent Ophion. They coupled and Eurynome laid the world egg which hatched the sun, the moon and the stars.

They lived together on Olympus and then Eurynome killed Ophion because he had become arrogant and then she went to create the titans and titaness to rule the earth and finally she created Pelasgus, the first man.

Now scholars find that the first, complete greek creation myth we are more familiar with in Hesiod's Theogony and Works and Days at around 800 BCE features a lot of similarity with the Pelagesian myths. It has been suggested that the the mythological changes reflects the development of Greek culture: According to these theories, in pre-Dark Age Greece would have been dominated by an agricultural society that emphasized the great mother goddesses, Eurynome. But then as it developed, a more warlike and patriarchal people invaded the peninsula, bringing with them their thunder‐bearing head god, arguably Zeus, and put an end once and for all to the ancient struggles between Earth and Heaven, female and male power.

Note however, that according to Hesiod's work and Homer's work there's no clear consensus as to who created mankind. Hesiod references "men of Iron" who Zeus made to replace the "men of Bronze" which were a warlike race that he buried in Hades. We also have the "golden race" made by Kronos , "the silver race" made by the rest of the Olympians and the "race of heroes" made by Zeus who lives on the Blessed Isles. In later traditions, however, you will get the representation of Prometheus making man out of clay, but that is not from Hesiod's work as far as I can find.

At around 700 BCE you will find the Orphic Creation myth, based on the mythological Orpheus, which tells a story a cataclysmic battle between the Gods and Titans because the Titans ate the god Dionysos. And from the ashes of the vanquished Titans did mankind emerge, carrying the souls of the titans Dionysos.

So, as you can see this is a rather complex mythology to decipher and there are a lot of variants, creations myths and debate as to what is the representation to what.

But to answer more directly to your question in regards to the Greek aspect of humanity: These stories weren't meant to merely explain as to how humanity came to be, but rather to also impose a certain moral and philosophical explanation as to how mankind is how it were. They weren't just answering "who was the first human?"

Hesiod's tale of five races (gold, silver, heroes, bronze and iron) are believed by many scholars and argued by ancient philosophers like Xenophanes to be a cautionary tale of human moral decline as the principle thought throughout mankind's history. Gaining tools and learning agriculture was not meant to illustrate progress but only to illustrate further negative development of humans. Even attaining fire by Prometheus was a tale of the evil mankind happens upon by the wicked and fraudulent theft of fire by him.

Others, like Aeschylus the tragedian, would argue it's a tale of divine intervention and to give mankind a weapon against tyranny (Zeus) and allows man to ascend above an animalistic sense. Whereas Sophocles and Euripides say it is a cautionary tale of mankind's ascension but also potential for hubris and failure.

In the end, as I hope I've managed to argue for, it's greek creation myths has been used for many philosophies and ideas and traditions throughout the greek world. It has a lot of different aspects, depending on the sources we've found and the angle to which it has been debated on. I wouldn't say it is as clear as you might believe as to who created who, and in a way I think a lot of creations myths have a lot of similar factors to them.

For the Greeks though during the classical age it was a form of aetiology to try to explain more than "who created us" but also what it meant for us as human.

Sources:

Brill's New Pauly: Origin myths and theories on the origin of culture

Leeming, David Adams & Leeming Margaret Adams, A Dictionary of Creation Myths

• Pelasgian Creation

• Orphic Creation

• Greek Creation