"The fool hath said in his heart, There is no God..." Psalm 53:1a
This is the beginning of a Psalm of David. When reading the Psalms I think it would be fair to say that everyone would unanimously agree that the writers of the Psalms were sold out to their belief. You can just tell by the language that they use that they really believe what they are saying. David knew God by faith. His faith was such that he could and would call on God in many occasions to work with him on co-creating situations with a favorable end. David had already found out that God was real and that one minute in the presence of God is better than a lifetime of various mortal pleasures without.
When David says, "The fool said in his heart, There is no God," he was singing his heart out and making it clear that to even think there is no God shows how utterly ridiculous and ignorant some people are. Don't blame God. God has made it abundantly clear of His existence, through faith and through the things He created and sustains even today. You have to turn a blind eye to God to make the statement that there is no God. Quit worrying about other people with other faiths, that there must be something to their religion; after all God wouldn't let so many people just flounder in unbelief.
The Bible makes it clear that all creation points to God and that it is God's will that all mankind are saved, but God also created in us free will; free will to not believe His record and free will to close our faith eyes. Many people exercise that free will to deny God. Focus on your own faith and let God permeate your being the way He permeated Davids.
It amazes me that we are so high minded to think that God isn't fair, because He made it so hard to believe the truth and those of other major world religions haven't been given a fair shake. It is presumptuous to think this way and not true at all. God calls every person at every age, all nationalities and all levels of intellect. The Resistance of man to recognize God is pompous pride and blind ignorance. It's your job to testify of what God has accomplished in your life, not to try to figure out why God did it this way or that way.
I've learned to be thankful for the way God designed it all. I've seen what man can do when man is in charge: Hate, prejudice, terrorism, lies, forced religion, false premises, unnatural affections; the list is so long and none of it is good.