Some similarities are that both Islam and Christianity believe in the prophets such as Prophets Adam, Noah, Abraham, Moses, Jesus (Peace be upon them all).
They both share some moral values such as love thy neighbor, cherish life, feed the poor. etc.
Both are Abrahamic faiths, and are both monotheistic.
The difference lies mostly in how Jesus and Muhammad are viewed.
Christianity is a triune monotheistic religion. Its form of monotheism can be summarized in the following seven points:
1. The Father is God
2. The Son is God
3. The Holy Spirit is God
4. The Father is not the Son
5. The Son is not the Holy Spirit
6. The Holy Spirit is not the Father
7. There is only one God
Christianity rejects Muhammad as a messenger of God.
Christianity believes Jesus died on the cross and Islam rejects this.
Islam is a strictly monotheistic religion; it teaches that Jesus was a messenger of God, much like Moses, Noah, etc. God is one in Islam, with no partners or children. Islam also teaches that Muhammad was the last of the messengers.
· In Christianity, Jesus came and died for sinners as prophesied by the Jewish prophets. In Islam, Jesus did not die but taken to heaven.
· Love your enemies is the Christian teaching. Islam does not teach to love non-Muslims.
· Christianity has a savior Jesus Christ who saves them from sins and hell punishment. Islam does not have a savior but has only messengers who died just like regular humans.
· Marrying another person while your spouse is living is adultery according to Christian teaching. Islam does not consider this as a sin (following Muhammad's example).
· Christianity offers a heaven with the presence of Lord Jesus. Islam offers a heaven with milk, vine and virgins.
· Jesus is the Son of God in Christianity as revealed in OT. Jesus is just a messenger in Islam even though Jesus is unique in Quran.
· Christianity found in the New Testament has no rituals. Islam has a lot of rituals including reciting in Arabic you do not understand and kissing the black stone at Kaaba.
· Christians are called children of God. Muslims are the slaves of Allah.
· Christians worship God in spirit and no directional worship. Muslims worship Allah by turning towards Kaaba in Mecca.
· New Testament teaches Jesus is the only way to heaven. Quran teaches good Christians, Jews, Sabience will also go to heaven.
· Salvation is guaranteed in Christianity since Jesus died to save them. No guaranty for salvation in Islam.
· Do not kill is the teaching of Christianity as Jesus or His disciples did not kill anyone. Killing is allowed in Islam as Muhammad and his followers killed many.
· Salvation in Christianity is based on what God did through His Son Jesus who was punished for others sins. Salvation in Islam is based on human efforts.
· Christian Scripture teaches not to fight. Islamic scripture teaches to fight and Allah loves those who fight for Allah (Quran 61:4)
· Christian Scripture teaches God as Righteous. Islamic scripture teaches Allah as a Deceiver ( best of Deceivers - Quran 3:54, 8:30)
· There is no consequence if a Christian leaves faith (except hell). Will be killed if a Muslims leaves faith (No compulsion in religion is an abrogated verse).
· Christian Scripture does not change its message. Islamic scripture changes its message through what is called abrogation with a new message (Many times in Quran old revelations were replaced by new ones, Quranic messages were abrogated by Muhammad and such)
· Christian Scripture came through EIGHT different people. Islamic scripture came through just ONE person.
· Christianity teaches that only those whose name is not written in the Book of Life will be in hell. Islam teaches that even all Muslims will have to go to hell (Quran 19:71).