Just a point of clarification:
Siddharth Gautama, the first Buddha ("Enlightened One" or "Awakened One") is not a god, never claimed to be a god, and gave specific instructions not to worship him. The Buddha taught how to end our suffering and how to gain enlightenment, Nirvana, to stop the endless cycle of birth, death, and rebirth. When asked questions about whether there is a God or not, whether or not we have a soul that lives forever or not, whether there was a beginning to the universe or not, the Buddha refused to answer. The reason is because these things have no bearing on our gaining enlightenment or the ending of our suffering.
Siddhartha Gautama died and was cremated. His ashes were deposited into several site around Asia. You can visit them today.
I believe the Biblical character known as Jesus did exist. I believe that man was similar to the Gautama Buddha - he gained enlightenment around the ago of 30 and then dedicated his life to teaching people what he had learned. I believe Jesus' fasting in the wilderness is where he gained this enlightenment. Gautama obtained enlightenment after meditating for 24 straight hours under a tree.
Gautama was raised a Hindu and therefor used Hindu cosmology to help people understand his teachings. Likewise, I believe Jesus was raised in the Judaic religion and used its teaching to help the Israelites understand what he was trying to get across to people. Jesus claimed to be a son of God. He also taught that were are all sons of God, that is to say - divine in nature. I believe the Israelites had him executed for this.
I believe after Jesus execution there were opportunists who embellished on Jesus' story. Eventually Jesus was deified. Christianity was invented, adopted by the Roman Empire as a control mechanism, and imposed on the citizens as the official state religion.