Vespasian was not the first of the five good emperors.  Those would be Nerva, Trajan, Hadrian, Antoninus Pius, and Marcus Aurelius.

Perhaps, but don't you think it was important to the people of the Roman Empire to know or be very curious as to where their "gods" were born? Also, I would imagine there had to be some type of hereditary legitimacy. So in that aspect it was important to know where an emperor was born.  In order to prove who his parents were, one needs to know where he was born. What if it was found he was born in Africa or Syria?  Then his lineage would be in question.

Actually, I wonder if this was not one of those modern Schliemann examples of an archaeologist making a find and attributing it to the most famous source even when the facts are inconclusive about it.  From the sound of the story the villa could have belonged to someone else.

scout, I meant if he claimed to be born in a particular place yet it was found out he wasn't, that could cause problems. 

I don't think so. It was part of their 'being' as an emperor as well as the state religion of Rome.  I think the more honorary traditions were when members of the emperors family were deified.  That seemed more like a tradition to follow than an actual religion though (of course their were exceptions).  If I'm not mistaken, all the Julio-Claudian family was deified and I think that was part of the religion, but I don't know if those who followed had the same prominence.

I think Augustus was the only one though.  My textbook says he never declared himself anything, he let others do that.  Other emperors were a little more egotistical.I'll try to paraphrase something about the Pantheon, so hopefully I'll still be clear.Hadrian was into one of the sun gods (forgot the specific name. Helios I think).  He built the dome of the Pantheon in order to symbolize his close intimacy to Helios and to the father of the sun gods, Zeus.  Many books use the word symbolism, but I think it was much more than that.  It was a real belief of his and probably many of his people. It was for a similar reason he completed the temple of Zeus Olympios in Athens.   I think many authors underemphasize the importance of religion to the Romans. I use the massive number of temples and other religiously significant monuments as evidence that religion was extremely important.

Wasnt it Voltaire that said something like "religion is mere tonic to the masses"?  I find it hard to believe that the Roman elites took their religion so seriously at the end of the Republic.  Especially so given the amount of religious assimilation they engaged in.  They had cults to just about every god and pantheon in the Known world in Rome.  I think they cynically used the state religion to further political goals.  It is clear from early imperial history that Caesar and Augustus at least understood the power and influence they got from holding high religious office.

I think your original question about deification being an "honorary" thing, and then the subsequent discussion bring up larger issues.  Did Romans actually believe in Roman gods?  Probably not completely but they do seem to have been superstitious.  They were heavily into ritual which had to be done just right in order to "work".  They respected that which was "old" and despised that which was "new".  As a professor mentioned, this is why the Romans despised Christianity but not a non-pagan religion like Judaism (it was never the case that a person could be put to death for publicly stating he/she was a Jew, but one could if one stated he/she was a Christian).I know there were temples to various emperors in the Roman Forum area, including the temple to Augustus, and I think temples to Trajan and a few others.  I know that after deification, at least one emperor used it as a means to claim that he was the "son" of a god so he had greater authority.I can't remember the exact details, but I recall that in one of Plutarch's texts on the history of Rome it was acknowledged how important religion was as a means of keeping society together.  It think the implication was that even though the Roman religion was not "true", it was still very useful.

I just get the impression that those at the top used religion, especially the state religion, as a tool to control the majority. 

I don't think they could have used religion to do that and I get a different impression in that the rulers accepted the individual cults and just adopted them as part of the official religion, but still keeping their identity. I think they kept control by laws and a military that assured the laws were followed.