Jesus was a Jew. He was born a Jew and he died a Jew. Christianity as such did not exist until Saitn Paul reinterpreted the death of Jesus as the salvation of mankind from the Original Sin that all human beings inherited from Adam. Thus, both Judaism and Christianity worship the same God. Of course both religions are very different since Christians believe that Jesus is the Messiah and the Son of God. Judaism is still waiting for its Messiah, although it did have four in the past in the forms of Moses, David, Solomon and Darius the Great (he is called a Messiah in the Old Testament even though he was a Zoroastrian Persian).

Islam arose later, out of Judaic and Christian beliefs among Arabs. The Prophet Mohammed reinterpreted both the Old and New Testaments. In his view (or rather that of Moslem scholars through the Middle Ages) Jesus was a prophet, but not the Son of God. All of the prophets of the Jews are also the prophets of Islam, and Islam also acknowledges Abraham as the first true prophet.

To say that the religions worship different Gods is wishful thinking. It is the desire to set each other apart, and it is born out of prejudice and fear. "There is no way my Christian God is the same as the Islamic God or the Jew God." It might appeal to those who are prejudiced and ignorant.

Of course, the first monotheistic religion was Zoroastrianism. The Chaldean civilization was an offshoot of the Babilonian civilization, and Abraham was a Chaldean. As such he would have been aware of Zoroastrian monotheism, and Genesis clearly points in some passages to the existence of other monotheistic tribes in ancient Judea.

Of course, it was the Zoroastrians who first personified good as God (Ahura Mazda) and evil as the Devil (Ariman). According to the Zend Avesta their epic war was waged for eons. Zoroaster predates Abraham by about 400 years, but neither Jews nor Christians nor Moslems acknowledge Zoroastrianism because that was the religion of the Persians, one of the dominant empires of antiquity.