The three major religions, as is spoken around the watercooler, is Christianity, Islam and Judaism. They are all pretty much linked together, and considered sister religions. This is because they all seem to believe variations of the same thing: that there were prophets on this earth (Adam, Moses, Abraham, David, Solomon, etc) and they were chosen to lead the people. The differentiations among them is that in Judaism they are still waiting for the next prophet, or messiah to show up, as foretold in the Torah, whereas Christians and Muslims believe Jesus was that next Messiah. The difference between Christians and Muslims is that the Christians believe the Messiah was also the Son of God, whereas the Muslims believe he was only another prophet in the line of prophets, and that God has no son. Furthermore, Muslims believe another final prophet, Muhammed came after Jesus (around 590AD), and he is the seal of the prophets, meaning no other prophet will appear to guide anyone.
Therefore, although Buddhism, Hinduism and Zoriastrism may have been around during the inception of these religions, the other three historically have been tied to each other geographically and in cross-referencing them with each other.