Ok, since a Muslim is writing this, it would make sense they don't see why there wouldn't be much difference. The issues where Muslims deny what the gospels and New Testament texts say about Jesus pretty much undermines what makes Christianity what it is. All the other stuff ends up, whether it be Adventists, or some other group, the basics of Jesus being the Son of God, and dying and returning is there (even in Mormonism and Jehovah Witnesses). Ok, this being said, here is where Islam ends up deviating from Christianity, and rendering Christianity pointless:
* Denial of the incarnation of God as man. This has multiple effects that make the Christian message not work. First, a Muslim will end up saying man is not made in the image of God. Islam says it is wrong wrong, eventhough Genesis says it is. The idea of people being children of God is foreign in Islam. God is not Father, God is Master. We are just his servants. And God has no sons according to Islam. No way Jesus is even the Son of God.
* The focus of Islam is on submission, not love. One can say one loves God in Islam, but that isn't the core. The core is submission, and obedience (Islam mean submission). Christians submit out of love to God. Also, love for others also stems from humans being made in the image of God, and being like God, and this love being a reflection of what one thinks of God.
* Islam denies the death of Christ, and with it, the resurrection. In Islam, Jesus is considered sinless, but there is no way a just God allows a sinless prophet to die. Death and sin are not overcome through the death and resurrection of Christ. There is no victory.
* Islam speaks of personal Jihad people do to overcome sin and temptation, but there is NOTHING about the human condition having issues that makes this battle not really doable without God's help. There is no imparting of the Spirit of God to empower a person to overcoming sin. And there is NOTHING resembling the western Christian concept of original sin either, or the Eastern tradition that humans are under a curse (a bit different from original sin). In Islam, everything is because of faulty texts. If you just give people the perfect text, the Qu'ran, then the issue of overcoming sin will be dealt with just fine.
* Jesus, AT LEAST, needs to be THE Messiah in the Christian faith, and this be understood. This is understood to be savior, and deliverer. In Islam, yes Jesus is The Messiah, but no one knows what it means. People speculate what it means, but there is argument that it doesn't mean savior, because God alone saves. Calling Jesus Lord would likely be straight out also. Without having a clue what Jesus as Messiah means, it is hard to do anything resembling Christianity.
* Lastly, the Old and New Testaments are considered corrupted in Islam. I would be interested in seeing a Muslim take the New Testament text and blot out those texts that are wrong and see what is left. Not sure much would be. Also, the question of why the Quran is perfect, but the other texts aren't also begs the question also. of how that would work.
So, on the surface, it would seem they are similar. But, by making Jesus an unessential and an afterthought just touched on in the Quran, makes it really hard to considered they are similar. I also think a Muslim would find it outright weird to think of a group of some people of The Book, to be part of Christ's body. After all, why would a prophet have a body made up of people of the Book.
