1. God wants all men to be saved:
1 Timothy 2:4 Who will have all men to be saved, and to come unto the knowledge of the truth.
2 Peter 3:9 The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance.
2. Mankind reveals himself to men in 3 main ways
A. General Revelation
Romans 1:20 For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:
Psalm 19:1 The heavens declare the glory of God; and the firmament sheweth his handywork.
Simply put, God reveals himself to mankind through creation, the creation around us testifies to the existence of a supreme being.
B. Revelation of Conscience
Romans 1:14 For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves:
15 Which shew the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another
God reveals his righteous character through man's conscience,
all people know murder is wrong, rape is wrong, stealing is wrong, etc.
C. Revelation of the Scripture and the Gospel
15:1-4 Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;2 By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain.For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;And that he was buried, and that he rose again the third day according to the scriptures:
So from this we can get an answer to your question:
God wants all men to be saved, he does not want any to die and go to hell, God must reveal himself to mankind through creation and conscience first, if a man will respond to this revelation, then God will reveal the Gospel message from the bible to them, and if they accept this and believe it, then they will be saved.
HOWEVER, if a person refuses to respond to the revelation of creation, For example they refuse to believe in any kind of God (Atheism), then God is under no obligation to allow them to hear the Gospel message, or if they refuse to listen that voice in their conscience telling them there is a God who they will be accountable to, then he is not obligated to allow them to hear the Gospel.
Basically if someone dies without hearing the Gospel message, it's because God knew they would not accept the message anyway.
Think about it this way, If you were a teacher and your students refused to allow you to teach them addition or subtraction, your not going to waste your time trying to teach them how to do algebra.
Hebrews 11:6 But without faith it is impossible to please him:
for he that cometh to God must believe that he is, and that he is a rewarder of them that diligently seek him.