well, if you would like to get into the nitty gritty of which stories it fits, keep this in mind: to have a story survive would mean SOMEONE witnessed the story (or we had more advanced scientific research back then, which would still make for a Young Earth, as they all believed in one)
i think the simple fact that all but the Chinese got in on this type of Creation shows you something. you can either assume they all knew each other at one point, and made small changes over time (small, despite it being "tens of thousands of years") or they all witnessed something similar.
My entire point being that to say one story has more basis to reality than another is a bit premature at this point and may miss a greater truth altogether. A frozen ice comet has more to do with the Norse mythos of Ymir, a frost giant, than it does with the "firmament" being divided by divine edict.
As for who witnessed some of these events. In most of them, aren't they handed down by the Gods themselves? In all likelyhood, they were either made up from whole cloth, or mutated over generations from events that were old when our ancient myths were young.
Until we figure out a way to peer back through time and witness events first hand, all we can do is guess.
I'm not trying to make the original post fit a "story". I simply posted the truth of Creation as given by God.