What about those who never hear of Jesus?

My answer to this question is that God will treat them fairly. Where we probably disagree is on what constitutes fairness. In evaluating the fairness of it, I would just have two questions:

1. Did they know the good they ought to do?
2. Did they do it?

I think everybody has an innate sense of right and wrong that is less than perfect. That means everybody is culpable for their behavior at least to some degree. If you know the good you ought to do (or the bad you ought to avoid), and you don't do it, then you are blameable. That describes every single person who ever lived long enough to reach some measure of moral awareness with the sole exception of Jesus Christ.

The gospel of Jesus is not that by becoming a believer you can turn your life around and stop sinning and therefore earn your salvation. It is rather that instead of being justly condemned for the sins we all commit, that we can be declaired righteousness because of our trust in Jesus and what he did for us. Jesus died to atone for our sins. We can be pardoned for our sins, forgiven, covered, washed in the blood of the lamb, etc. By being declared righteous, we can have a restored relationship with God and obtain a resurrection to eternal life. We can be rescued from the punishment we deserve for our moral shortcomings. We can bask in the glory of God and enjoy him forever.

Salvation is an act of mercy on God's part--something freely given purely out of God's love and grace. It isn't something bestoyed out of obligation, fairness, debt, etc. God doesn't owe salvation to anybody. So nobody who is punished for their sins, whether they've heard about Jesus or not, has any grounds for complaining that God is treating them unfairly. If they knew the good they ought to do, and they didn't do it, then God is perfectly fair, just, and righteous in holding them accountable and punishing them in proportion to the severity of their crime.

This is precisely why evangelism is important. Nobody can put their trust in Jesus if they've never even heard of him or have heard of him but know little or nothing about him.