The two religions are significantly different, even though Jesus Christ appears in both holy books. These differences can be observed by anyone. It is a fact that the call to make war on unbelievers is repeated over and over in the Qu'ran. It is this aspect of Islam that is strictly interpreted by Islamists that allows Muslim extremists to commit terrorism to win favor with God. In fact, they do not actually interpret it, they take it literally as it is written - the word of Allah.
Islam is really a beautiful religion except for the calls to make war, the admonitions against any innovation, the admonitions against financial loans with interest (integeral in modern economies) condemning them as haraam, or against God, and other beliefs that do not fit in with today's family of man. You will never, ever, see a Muslim extremist astronaut. Or a Muslim extremist scientist who discovers a cure for some disease. Or a Muslim extremist win any nobel prize for a scientific achievement or the Peace Prize. Yet I can envision fundemental Christians doing this. Some already have. The Western Muslims who have adapted to our society interpret these things differently than the Islamists, which allows them to adapt Islam to modern life in the world community. In Islamist's eyes, this makes them no better than kufr, maybe worse.
There really are no parallels in the treatment of "nonbelievers" that I know of in the holy books of Christian, Buddist, Jewish, Hindu, or any other religeon. It is true that many people have been killed in the name of religion, but none of the holy books, except the Qu'ran, call on believers to either convert or kill non-believers.