They all worship the same god. It's just the prophets that they follow that make the noticable differenece. Each time a new prophet shows up they get a following and the worshippers of their predecessors deny their divinity. Jews follow the older prophets, Christians follow the older prophets plus Jesus, Muslims follow the older prophets plus Jesus plus Mohammad. There are other religions that follow other prophets. Aten.. Zoroaster.. the Gurus.. and Bahá'u'lláh.. I can't thing of any others but I'm sure if you search around you'll find more.