What about people who have never heard of Christ?
The Bible makes it clear that through nature and conscience each person has some knowledge about God and sin for which he is accountable. (Read Romans 1:18-2:16.) Thus, everyone really knows, if he is honest, that God exists and that to ignore Him has serious consequences.
Christianity teaches that one is condemned for continually rebelling against God (Nahum 1:2-6, Psalm 90:7-8, Matthew 12:31-32). But the Bible also teaches that God is fair as well as just (Deuteronomy 4:29, Jeremiah 29:13). If you earnestly seek him you will find him. Ultimately only God can judge as only He knows the individual's heart.
Another way this question is often phrased is, "What about the innocent natives in Africa?" The truth is, there are no innocent people. The Bible teaches that we are all imperfect, selfish, weak, sinful, and spiritually unclean. We are dead in our sin and deserving of God's wrath (Ephesians 2:1-10). (For a more thorough examination of this, see our Christian Cram Course.)
On the one hand, we are confident that God will not hold anyone accountable for any knowledge he did not receive. At the same time, the Bible emphatically states that Christ is the only sure way to salvation. Anyone who has heard of the saving grace of Jesus, and rejects it, would be thumbing his nose at God (John 3:36).
To reject Jesus is a serious matter. It is tantamount to refusing God's offer of reconcilation to sinful man. As R.C. Sproul points out (book, noted in the resource list), those who have heard and reject Christ face double jeopardy. That is to say, you would be guilty by your sinful nature and also for having rejected God's son. Thus "religion" without Christ does not redeem people but may add to their ultimate guilt.