While Jesus himself was sent "only to the.....house of Israel" he commissioned his disciples to preach (reveal) the kingdom message to all mankind. That message is being preached globally by many ministries as we speak. You have probably even heard of it. It is a message of hope and peace (after the end time wars of course). Islam's 'gospel' seems to be fear and death.
The Christian Gospel is very much a "turn away from your sins, accept His plan for your salvation and you have nothing to fear. They can kill you, they can cause you pain, but your soul is safe in Him and everlasting life awaits after your time on Earth is done". And also, that Christ defeated sin and death at the cross by raising back up from the dead three days later.
But of course, Islam denies that (while saying the OT and NT are 'perfect, irrefutable' words of 'Allah').
Then, to reconcile that, they say that our NT isn't the same NT that was written back then (even though we have many manuscripts that say otherwise). You'd think a core concept like Jesus rising from the dead didn't suddenly get added into the NT after the fact, but apparently that's what they say.
I challenge a Muslim to point out one authentic early manuscript of, say, the Gospel of John that disagrees with the Gospel of John found in the KJV. John was very, very, very heavy on the deity of Christ, because it is so important. If someone doesn't believe in the deity of Christ... there's no hope for them whatsoever.
It doesn't matter what kind of prayers you say, how much you try to avoid sin, if you don't believe in the deity of Christ, then the truth is not in you, and His work on the Cross means nothing to you.
(note: All 'yous' are hypothetical and aimed at no one in particular)