There seems to be an interesting factual question lurking here: how much of the mythic overlay would people reinvent in a similar form, even if they forgot all their language and culture? A quick search turned up the amazing Wikipedia page List of thunder gods. Of course, the major monotheistic religions are also very similar to each other (I'd say about as close as C# was to Java when it first appeared), but they didn't arise in ignorance of each other, as pagan mythologies did.