This is a perfect example of how easy it is to make God sound like a monster by wording a question in just the right way.
For starters, NO ONE winds up in hell simply for failing to acknowledge God. (Even Christians fail to acknowledge God sometimes.) Hell will be populated by people who vehemently reject God—who say, "I want nothing to do with God or His Son. I refuse to turn from my sin and I reject God and all that He stands for."
Secondly, you need to understand that hell is never God's intended destination for anyone! (In fact, we're told that originally hell was created for the devil—not for man.) The Scripture clearly says that God is "...not wanting anyone to perish, but everyone to come to repentance." 2 Peter 3:9 (NIV)
People have to literally choose hell over God's offer of forgiveness through Jesus Christ.
You see, Jesus laid down His life for sinners. He suffered terribly on the cross, bearing the condemnation that we deserved. He didn't have to do any of that. But once He did, He made forgiveness freely available to ANYONE who would humble themselves and ask. To reject that free gift of forgiveness is to throw away any chance of being saved! Why? Because, as Jesus said: "I am the way and the truth and the life. No one comes to the Father except through me." John 14:6 (NIV)
It is only by REJECTING the work of Christ and what He accomplished for us on the cross that people put themselves in danger of hell. According to Merriam-Webster, the definition of reject is:
: to refuse to believe, accept, or consider (something)
Hell will be made up of those who looked at God's free gift of life and said, "I'll pass."
The follow-up question to this one is: "What about those who have never heard about Jesus or God's love?" And the answer to that question comes in two parts. The first part comes from Romans chapter 1.
[God's] invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse. Romans 1:20 (ESV
This passage tells us that God has revealed Himself in all that He has created. So even if people have never heard, there is a judgment based solely on a person's response to all that he or she can see in this world and beyond. The creation infers that there was a Creator behind it all. This evidence in creation is so profound that the Apostle Paul said men are "without excuse" as to their determination of God's existence.
But the second part of this question is bound up in our understanding of the character of God as revealed in the Scriptures. (Usually, people who ask this question are either unfamiliar with God's character or have doubts about Him.) But to know God's character is to forever settle this question in the heart of the worshipper.
When Abraham was told by the Lord that Sodom and Gomorrah were about to be judged for their sin, Abraham began to fear for his nephew who lived among the wicked people of those cities. He finally asked the Lord, "Will not the Judge of all the earth do right?" (Genesis 18:25)
When we ask questions such as how God will deal with those who have never heard the Gospel we're essentially asking this very question: "Will not the Judge of all the earth do right?" And the answer is, "Yes! He will!" Since God is perfect in all His ways, that means His judgments will be perfect and without error, His compassion is perfect and untainted, and His love is perfect and unselfish.
God makes no errors. On the day when men stand before the justice of God's eternal holiness, there will be no accusations of unfairness or injustice. All things will be done in the perfection of His character.