The Serpent is Prometheus, Loki, and Enki, while God is Zeus, Tyr/Odin, and Enlil, in the early Bible.
Enki was given dominion over Africa, while Enlil was given dominion over the Middle East - as a result, Semitic religions (i.e. Judaism, old Christianity, and Islam) all favour Enlil over Enki, while non-Semitic religions often favour Enki over Enlil.
Enki is the God who first helped to shape Man into what Man is today. Enki gave Man fire, the wheel, agriculture, civilisation, medicine, religious practice, writing and language, and many other things. Enlil is the God who seeks to keep Man in his place, subservient to God - he gave Man the deluge (Biblical Flood), the destruction of the first civilisation (Sodom and Gommorah, which actually ended up destroying the entirety of the Middle Eastern civilisations, excluding Babylon), the confusion of language, and so on. Enki and Enlil are eternally at war with each other, even though they are brothers.
The parralels to Greek mythology should be clear - Prometheus teaches Man to confuse Zeus as to which of the potential offerings has the most good meat in it; Prometheus teaches Man the secret of fire; Prometheus acts as a friend to Man. As a result, Zeus, the "King of the Gods", punishes Prometheus, the Elder and more ancient being. Exactly the same thing is happening in the Enki/Enlil story (Enki arrived on Earth before Enlil, but, because of his slow process in extracting gold from the Earth's crust for use by the Gods [this is never explained], Enlil was sent down to rule over the Earth instead, at a much later date). We can't be sure how the Norse saw Loki, for, although he is portrayed in the surviving literature as an enemy of the righteous Gods, we must understand that the surviving literature was written by Christians, not Pagans, and so is more likely to favour the "Gods" over the "Titans/Giants/Elders", as Odin/Tyr corresponds to God/Allah/YHVH. Loki is always the one who ends up helping the Gods out, in the end - for example, he tricks the Dwarves into creating Mjolnir, Thor's Hammer, one of the most powerful weapons of the Gods.
If we take the Sumerian myth and transpose it over the relevant bits of Genesis, we get a distinctly interesting view of Eden. Rather than the fabulous paradise created by God, E.DIN (the Sumerian name - Genesis, and the Bible in general, takes almost every single one of its stories from Sumerian myth, excluding the huge family trees, which are simply historical recordings) was a fertile land where Enlil took some of Enki's humans and put them to work planting the seeds of every tree and plant known to exist in the world. Enlil tells the humans that they may eat of every tree in the land, except for two - the "Tree of Life" and the "Tree of Knowledge". Enlil threatens Death to those who attempt to do so. Enki ("the Serpent", "the Adversary", "Shai'tan") comes along and tells his humans that this is, actually, a complete lie - Enlil doesn't have the power to kill the humans in such a way. He tells Man to eat of the Tree of Knowledge freely, without fear. Man does this, and Enlil is enraged at their disobedience - he throws Man out of E.DIN, sending them all back to Enki's land (where they came from originally, anyway).
And so you have it - our Biblical story of the Garden of Eden is a pro-Enlil rewrite of the original Sumerian myth of Enki's men being stolen by Enlil, to work for his benefit rather than Enki's. Given other descriptions of the differences between Enki and Enlil throughout the Sumerian histories, Enki was a far kinder and more caring "God" than Enlil - mainly because he was, in effect, the "father" of all humans, seeing as how he and his half-sister, Ninti, had taken the primitive Homo Erectus and worked some magic [i.e. genetically modified them] so that they evolved at an unnaturally fast rate, to become Homo Sapiens. This curious Sumerian myth actually explains the "missing link", and also explains how millions of years' worth of Evolution could happen in the 100,000 year period between the emergence of Homo Erectus and the supremacy of Homo Sapiens. For all you Atheists - basically, God did it!