They can all be right and all be wrong. If God is so incomprehensible, then no man will have it exactly right, but will have bits and pieces right. On the other hand, there may be no God, in which case they are all wrong.
Muhammad is dead....Joseph Smith is dead....etc. etc. We have a risen savior. ..... All which He said He would do He did....all which He says He is HE is.....and all which He says He will do you can, with certainty, know that He will do in the future
Their God is not dead. Unlike Jesus, their Mohammad, Moses, Joseph Smith, Buddha, etc were not gods, so they are dead.
Some religions are just naturally nicer, just like some people. They are more inclusive and less radical. Islam is a rabid and extreme, opressive religion, unlike just about any other one these days, but Judaim or Cristianity were not much better in the past.
We owe much of our tolerance and "niceness" to the Age of Reason and the humanist freethinkers of the later 17th, and the 18th centuries.
When you say to "Christ is within us" that sounds wonderful but it is not obvious or compelling. Other people are willing to die for their faith. Many a Christian used the martyrdom of early Christians as proof that their faith is true. So who are you to tell others theirs is not true if they are dying for it?
It wouldn't be to those who cannot relate. But it is nonetheless the difference between Christianity and all other religions, and since Christ abides in us it is quite compelling and obvious to those who know this.
If God is so incomprehensible...
He's actually not incomprehensible to those who know Him.
So who are you to tell others theirs is not true if they are dying for it?
People can and do give thier life for many things...not just religious reasons. So this certainly isn't a consideration for how I might view another religion as true or false.
Some religions are just naturally nicer
There are many people who are 'nice' without any religious affiliation. So this wouldn't affect how I might guage what is truth.
Their God is not dead.
Well in that regard one must then determine if or not the God they claim is the same God of Christianity.