Everyone has what they need to respond to God. No one goes to hell because they have not heard about Jesus – they lose out on salvation because they are sinners that fall short of God’s standard and openly rebel against the God they know exists.
There are two things we must consider in trying to answer this question. First, everyone is accountable to know that God exists. For we read in (Romans 1:20): “For since the creation of the world God’s invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that people are without excuse.” Based on viewing the complexities of our world we can clearly infer that God exists. Therefore, even those who haven’t heard about Jesus are accountable for knowing that God is. Second, we are also accountable to know that we are sinners. In the Old Testament we clearly see how we can’t keep the law. But the New Testament also show us that our conscience and heart also inform us that we are sinners for we read in (Romans 3:20): “through the law we become conscious of our sin.” Everyone knows basic right from wrong and has their own moral standard in their heart with or without knowing the specific laws of the Bible.
Therefore, since we all know that God exists and that we are all sinners, even without knowing if Jesus exists, God will hold us accountable to humbling ourselves before him. Even the Old Testament saints were saved by faith in God and by humbling themselves before God; and this was before Jesus came on the scene.
Knowing that God exists from nature is called general revelation. Knowing that Jesus exists from the Bible is called special revelation. I believe that all people have general revelation and those people who may never have heard of Jesus, say a remote African tribe, if they truly seek after knowing who God is will somehow be given the special revelation they need to be saved. Some of the many ways that God can do this is by sending a missionary to our remote African tribe, sending an angel with the message of Christ, through dreams and visions, and through the Holy Spirit working in other miraculous ways. For example, it is estimated that in Muslim countries thousands of people have come to Christian faith through Jesus revealing Himself in a dream or vision to them. So, if someone is truly seeking to know God, He will somehow reveal Jesus to them. In the final analysis God holds all of us accountable to the light we have and to the light we are seeking to know.