The most offensive element of the Gospel and the most common objection to Christianity is the idea that Jesus is the only way. In this age of religious pluralism, it's the first claim jettisoned when Christian groups get the itch to become more "tolerant."
There are really four different questions here, all answered in this teaching: Does the Bible teach Jesus is the only way? Why is Jesus the only way? What about other religions? Won't good, moral, sincere people go to heaven, too?