I am speaking salvation in religious terms here.
In many conversations with my Muslim and Christians friends the topic of salvation is an important one. Understandable really, when one believes that the whole purpose of our earthly being is about 'getting it right' and doing/believing the right things to get you into paradise.
I know Christians who believe that anybody who has not publically declared that Jesus is their Lord and personal Saviour is not saved and will not go to heaven.
Equally I know Muslims who believe that anybody who has not said Shahadah "Lā ʾilāha ʾillā l-Lāh, Muḥammadun rasūlu l-Lāh (translation: There is no god but God, Muhammad is the messenger of God) has not accepted Islam and will not be granted entry into Jannah (paradise).
I have been around for long enough, have observed people often enough and have had enough conversations to be convinced that there are people from all religions and none who are closer to God than many of those who are convinced to follow the 'true religion' (whichever that may be) would like to think. And that we are foolish if we think we know you is and who isn't saved, simply by what declaration they have made.
Ultimately we do not know. We are not meant to judge. We are meant to live our lives to the best of our abilities and be the best we can be - and leave others to do the same.
I came across this picture and quote, which just about sums it up. I love the image of Jesus sneakily pulling people over the wall. :)