Historically we know very little about the Buddha. Even to this very day, debates still occur as to the dates of his life and death, although most scholars tend to agree that the Buddha lived for around eighty years.
There is archaeological evidence such as, monuments, inscriptions and there are the Sanskrits; this leads me to believe that there is a very distinct possibility of his existence. Most of the accounts of his life are very similar and only alter in certain aspects of the tale and not in the main structure of the story. There are many many accounts from many parts of the world; I would have thought that there would have been a lot more discrepancies between the differing versions, considering how far apart they may have originated from.
Like all accounts of history, we depend on information being passed down, mainly through written evidence and tales of myth and legend. The problem with this is that legends are altered through time, key aspects and facts are changed slightly or sometimes significantly altered (Chinese whisper syndrome).
The myths probably do more damage to the credibility, some of the reports of Siddhattha being born at six months old or his mother becoming pregnant by a six tusked elephant are very hard to stomach. Although there is symbolic belief; with regards to the elephant being strong, wise, having the durability to travel and being white, a direct link to purity.
These changes could have been made in order to give the person or the faith a better image, or there might not have been any changes whatsoever and the story has survived for 2’500 years completely intact. This is very similar to the stories told in the bible about the conception of Christ and the development of Christianity. But at the same time, you could say that there is no smoke without any fire?
At the time of the Buddha’s life, there was much upheaval within India; both political and religious aspects of the country were undergoing change. People were cut off from old sources of order and were therefore perhaps ready for change and happy to oblige to the Buddha’s ideas. Another important factor was that women were allowed to follow this religion; this meant that it had a huge potential with regards to numbers.
Buddhism was nearly wiped out during the 12th century because of military conquest. Maybe, during that time, important pieces of evidence were lost, destroyed or even stolen and never to be found?
All in all I feel that the odds are stacked in favour of his existence, simply due to the corresponding stories. If you try to read the main structure of the story and take the exaggerations with a pinch of salt, it all seems a very feasible part of history.
We seem to know little about the Buddha of history and his existence; with the development of science things are bound to change and more information will become available to us. One thing is for sure, we do seem to know more about the Buddha of story.