It's an awkward situation because usually the person asking the question is looking for a one word answer, but a one word answer gives a completely wrong impression. The question runs something like this, "Do you believe all _________ (fill in religion here, such as Muslims, Jews, Buddhists etc.) are going to hell?" I have heard this question a few times. I was asked it recently - the questioner had heard the Gospel and, with tears in his eyes, he asked me if he was going to hell because he was a Muslim. I heard it in a radio discussion between a Jew and a Christian. The host of the debate put the question to both participants - "Do you believe the other one is going to hell?"
Answering "yes" to that question without further explanation just makes people think Christians think they are better than everyone else, after all, that's what determines who goes to heaven or hell isn't it? So if Christians think they're going to heaven and no one else is, it just shows how arrogant they are. Perhaps you think the same? I want to tell you what I thought was wrong with the way the Christian answered the Jew, and then I'll tell you they way I tackled the question with the Muslim (for what it's worth).
The Christian who was engaging the Jew was feeling the pressure when the host asked the question, but he said something to the effect of, I'm bound to say, in light of the Scriptures, that a relationship with Jesus Christ is essential." OK, he is bound by the Scriptures to say that but he made it sound as if he couldn't really understand or explain why that should be. He sounded as if he was a bit confused and perhaps slightly embarrassed by this clear Scriptural requirement. If he had have listened to the way the Jew answered it might have helped him. The Jew said that any righteous person will be accepted by God. With that the New Testament would agree (Romans 2 v 13), but the problem is (as Paul goes on to show) that we are not righteous - we are all law-breakers, and thus guilty and condemned (Romans 3 v 10, 19-28), and that is why we need a Saviour and a Substitute, i.e. that is why we need Christ.
When I was talking to the Muslim he wanted to know was he going to hell because he was a Muslim, I told him no, he would be going to hell no matter what religious label he had. I told him he was going to hell because of his sins, and for that reason everyone is going to hell, and that's why he needed to put his faith in God's provision for his sin, i.e. Christ.