They all believe in one God, and there are similiarities between all three. They all have some basis in Judaism, ironically enough.
The Jewish religion goes back around 4,000 years. Its patriarchs were Abraham, Isaac and Jacob. Abraham's people were polytheistic, and he questioned the worship of idols. He believed in one Creator. He was called by him, and if he chose to leave his home, He would make him a great nation. Israel was this country. They believe in the Messiah, who will redeem the world and restore the Kingdom of David.
Christianity goes back 2,000 years and is based on the teachings of Jesus, who they accept as the Son of God. They believe Jesus was/is the Messiah, and believe He will come again and redeem the world.
Islam goes back around 1,300 years. Its mainprophet is Mohammed who was a trader. Not unlike Abraham, he questioned the polytheistic practices of many of the people around him. He was visited by the angel Gabriel who told him he was to be the prophet of Allah, the one true God. He was told of earlier, lesser prophets that came before him, such as Abraham, Moses, and Jesus. To Muslims, they were prophets that helped prepare the world for the Koran, the true word of God. Because of them, certain books of the Torah and the Bible are divine. They reject the idea of the Holy Trinity as blasphemy because it puts Jesus on the same level as Allah or God. They believe in a redeemer as well, known as the Mahdi.
They have a different set of social standards, and set forth different a different basis for salvation.
They all pretty much acknowledge Jesus, but have different views of him. To Christians, Jesus is a divine figure, the Son of God. Muslims acknowledge Jesus as a prophet, but reject any notion of His divinity because only Allah is divine. Jews generally see him as a human, period. A profound rabbi, or teacher, but a man. Some considered him to be a radical, breaking with some traditional orthodox views. They reject Him as the Messiah because the Kingdom of David was not restored, and the world wasn't redeemed by His coming.
Israel is the ancestral home of the Jewish people, but they didn't occupy it as a nation until after WWII. At the time it was the nation of Palestine, which for a long time was a Muslim nation until the fall of the Ottoman Empire. In the early 20th century, the UK had started working towards a national home for Jewish people in Palestine. They were unsuccessful in the end, and passed the reponsibilty of solving the problem of Arabs and Jews coexisitng in Palestine to the UN. In the end, Israel was granted recognition as an individual nation in 1948.
The problem there is, Israel is vital to both of their religions. Sites throughout the country are considered holy to both. Israel has sites that were the temples of long ago. It's also the place where Mohammed is supposed to have ascended to heaven. Because of that, it isn't just differences in religion, but also a matter of territories that are important to both their spiritual heritages that cause the conflicts. Radicals use the religous differences as the basis for their cause.
Beside the fact that they're largely Christian countries, Great Britain and the US are seen as primary enemies because they're considered to be two of the biggest supporters Israel has had since its re-establishment as a nation. It's basically because of GB that Israel as a nation came to be. The US has basically always supported Israel for multiple reasons, not the least of which is they're a strategic partner in the Middle East. We're also hated because of the Camp David peace accords of the late 70s with President Carter, Anwar Sadat, and Menachem begin. Anwar Sadat was assasinated because of that.
The sad thing is, all three religions are based on a philosophy of peace and love and peaceful coexistence when you get right down to it. It's the hard liners that cause all the conflict.
