The important difference... the one that counts... is, in Islam, Jesus is known as a great prophet. Period.
In Christianity Jesus is known as God in the form of a man.
In Islam, Jesus doesn't save anyone. Your works and your piety are what saves you.
In Christianity, works and piety are never enough. Jesus God in the form of man saves through His perfect life, and innocent suffering and death on the cross. And the seal - the proof - is that he arose from death, and later ascended, physically into Heaven. He could save us because it would take a God to make perfection out of imperfection. We can never do this ourselves.
The promise of Jesus to people is that if they believe in His works and what He did for us, and believe the promise that He will save all who ask Him to, he will save all those who so believe. In other words, Jesus God did the work for us that we can't do.
This, above, is the great foundational difference between Islam and Christianity. All the rest of the religions pales when compared with this difference.