Islam, Christianity, and Judaism are remarkably similar. However, there are some fundamental beliefs that are very different between Christianity and Islam. One problem in inter-faith dialogue is the fact that there is still a lot of ignorance about what it is Muslims believe and how it differs from Christianity. Many Christians in Western Europe and the United States, no doubt fueled by the anti-Muslim media, consider that Islam is completely alien to Christianity. This is absolutely not the case. Understanding exactly what the differences between Christianity and Islam are may help dispel the ignorance and myths that are the cause of much conflict between both religions. As in any discussion, it is important to understand your opponent's argument in order to have a debate, rather than simply attack blindly driven by blind prejudice.
The main point of difference between Christianity and Islam lies in the view of who Jesus (peace be upon him) was and what he did. Christians consider that Jesus (peace be upon him) is God's son, part of holy trinity that divides God into three distinct parts that at the same time form a single entity. Muslims consider these statements to be blasphemous. For Muslims, claiming that Jesus (peace be upon him) is deity is polytheism, pure and simple. Muslims reject the idea that God had a son. However, Muslims do believe that Jesus (peace be upon him) was one of God's messengers to mankind – one of God's last prophets. Muslims also believe in the immaculate conception and consider the Virgin Mary as the purest woman that ever lived. However, Muslims do not consider that she gave birth to God's son, but that Jesus (peace be upon him) was simply created in her womb because God is all-powerful and willed it so. Muslims also do not believe the that Jesus (peace be upon him) died on the cross. Muslims believe that God rescued Jesus (peace be upon him) from crucifixion and took him to paradise. Like Christians, Muslims believe in the second coming of Jesus (peace be upon him.)
Muslims also do not believe in the concept of an original sin. Muslims believe that all people are born in a pure state, with a clear slate. Muslims also believe that this state of purity can also be achieved by those people that repent and turn their hearts to God. The Muslim view is that it is through each person's actions that eventual entry into Paradise can be earned or denied. This is not to say that Muslims believe that faith is not important, only one's actions. Faith in God is a fundamental part of salvation. However, faith is nothing without actions and, in Islam, one's actions are extremely important.
-- Al Arabiya Digital