Hinduism, Zoroastrianism, Judaism, Buddhism, Christianity and Islam are the six great religions of the world. There is no founder for Hinduism. All the other religions have their founders. They are named after the name of the founder (except Islam). Jainism is only another form of Buddhism. Sikhism is based chiefly on Hinduism and partly on Islam. Brahmoism is born of Hinduism and Christianity and so on with other minor religions.
Whenever any important truth of religion was suppressed by the arrogance and selfishness of the priestly class or forgotten through the ignorance of the people, there appeared a great Saint or Prophet or Religious Teacher. He emphasized that truth, removed the dross which had concealed or obscured it and made it shine in its original brilliance, purity, splendour and glory.
In this way every new religion was only an endeavour to reform the older religion as it then existed and a protest against its abuses.
When in olden times people forgot all about the Vedic monotheism (Hinduism), there arose Zoroaster. He preached the worship of one God, Ahura Mazda, and condemned the worship of Devas (gods).
When the religion of the Vedas (Hinduism) degenerated into a blind observance of rites and sacrifices of animals, when the Sudras (servants) were treated with contempt by the Brahmins (priests), there appeared the compassionate Buddha, who stopped killing of animals and raised the status of Sudras.
When the priests of Judaism became arrogant, there arose Jesus to purify Judaism. When Christianity had also degenerated into idolatry and superstition, there appeared Mohammed to preach his monotheism.
Thus all great religious teachers were original reformers. They tried to improve the existing religions and to do good in their own way to suit the time and condition in which they were born.
Here is a compilation of what Gurudev Swami Sivanandaji Maharaj wrote about the great prophets who were born in various parts of the world.