Hi Marv.  Sorry for the late welcome (I'm a bit behind in reading posts).  However, the welcome is no less sincere.

As for your question, in The God Who Wasn't There, Dr. Alan Dundes gives some great examples of mythical gods (like Dionysis) that have very similar stories to Jesus. 

It is seems that the story of Jesus is very probably one more myth in a long line of similar stories. 

That's the view of the overwhelming majority of professional scholars in relevant fields who have studied the evidence regarding the origins of Christianity - that there was an historical preacher called Yeshua bar Yosef who was the origin of the later mytholgised stories.  The idea that he never existed at all is a fringe theory which is only subscribed to by amateurs like Earl Doherty.  It has zero respectability in the world of real scholars who work within the system of academic peer reviewed research.  And we're talking scholars who are atheists, agnostics and Jews here; not just fundie apologists.

 The most obvious and logical "causation" was that there definitely was an historical figure as the origin of the later stories.  The fact that those stories include elements that were actually rather awkward for the early Christians is one clear indicator of this. 

 For example, all the gospel accounts say that Jesus came from Nazareth in Galilee, despite the fact that the Messiah was meant to come from Bethlehem.  The writers of Luke and Matthew tie themselves in contradictory knots trying to explain how a guy who everyone knew was a Galilean from Nazareth could have actually be born in Bethlehem (and trip each other up in the process).  If Jesus never existed, why would someone invent a Messiah from Nazareth and then have to go to the trouble of explaining away his Galiean origins?  Why not just invent a Messiah from Bethlehem in the first Place, since Nazareth had zero significance in any messianic prophecies and no other significance at all?

The obvious answer is that they said he was from Nazareth because he wasn't a fiction and because he was from there.  This was awkward for people trying to sell him as the Messiah, but it was an historical detail that they simply couldn't leave out or gloss over.  Thus the stories about his family coming from Bethlehem originally (Matthew) or travelling to Bethlehem just before he was born (Luke).

Your post also hits one of the major flaws in this kooky "Jesus Myth" idea squarely on the head - if Jesus never existed, who invented him, when, where and why?  "Jesus Mythers" are never able to come up with answers to this key question that aren't indulgent exercises in implausible fantasy.

"Very similar" is stretching things quite a bit.  If you actually look carefully at those gods and their stories, there are actually very few parallels at all and even the ones that exist aren't terribly close.  This line of "reasoning" was first proposed by Kersey Graves' now thoroughly debunked and discredited piece of Nineteenth Century pseudo history.  Flemming's movie even has a list of the names of these supposed parallel gods that includes names that Graves' either made up or totally bungled.  Flemming now says he's going to release a new edition of the DVD that removes these errors, but the fact that he's using crappy Nineteenth Century crackpots for his "research" at all speaks volumes about the low quality of his rather feeble film.