Beleif or non-belief in religion ultimately boils down to the question of whether you think a god made humans or whether humans made gods. If you are in the former camp, then you pretty well have to be an atheist or at least an agnostic. There might be a few people in a fringe group who accept that humans made the gods, but who still want to believe they exist and worship them, but that would be an unusual position. If you think that human beings are responsible for creating all the gods, including the Christian god "God", then it is probably only a matter of time until you reject religion and embrace atheism.
So, how do we answer that question? As the old AC/DC song goes: "Who made who?" It's a question which cannot be proven one way or the other, at least scientifically. Since there is no way to disprove the existence of God scientifically, many Christians take that to mean that he must exist or that his existence is likely or even plausible. It is not. The scientific approach to things shows us no evidence for any gods. When there is no evidence for something in science, despite our best efforts to find it, it almost certainly doesn't exist.
Let's think for a minute about the option of God creating humans. While we have to allow that it is technically possible, it is more important to examine the question of whether it is a plausible concept. What would we expect if God had created the world and everything in it, us included? God is love, so say Christians. Above all else he is a loving god. It's all they sing about in their hymns. While sermons and lessons also include a fair bit about judgement and power, Christians almost all agree that their god is loving. Yet, what do we see through history and pre-history in terms of humanity? The vast majority of humans have died a premature, painful, and lonely death. All through pre-history, humans were mostly dying off as infants without a chance to enjoy anything in life. The few that survived to adulthood could expect a primitive, painful existence of hunger, disease, fighting off predators, and a death by age 30 at the latest. Is this really they system of life you would set up if you were an omnipotent, omniscient, all-loving god? Imagine you were sitting there with no universe in place yet. You get to choose everything about the universe. You can create it any way you want, and you can fine tune it any way you want. Plus, you get to foresee all the possible outcomes of any universe you decided to create before hand. You would go ahead and create one in which your chosen species, molded in your image, whom you loved so dearly you would sacrifice your only son for, that species would suffer tremendously every day? The newborns of that species that you love would mostly die off shortly after birth through some disease, caused by a microorganism that you also created. Really?
OK, so let's assume that God knows more than we do. Perhaps he knows that dying is actually the easy way out because it leads to heaven. Maybe he's actually doing us all a favour by creating a world where, for most of our existence we've scratched out a meager existence full of pain, disease and death. Doesn't that then beg the question of what about all those people who don't hear about Jesus (i.e. the vast majority of humans throughout pre-history and history). They all just get shuffled off to hell forever. Congratulations, you survived infancy and childhood, you lived to age 18 and then got picked off by a sabre-toothed tiger. But, unfortunately it is the nature of the universe that you now get to spend an eternity of pain and misery in hell because you didn't accept Jesus Christ as your personal saviour. So sorry about that. Does this sound like the all-loving Christian god?
Let me pause at this point and state that I am aware that many or most Christians would object to this line of characterization of their religion, that I am focusing on things that are not really relevant or part of their loving god. Jesus is all about love and forgiveness, he brought light and salvation to the very dark and cruel world that I've just described, right? Well, to me that attitude it nothing more than a particular brand of patriotism. I hate patriotism because it blinds people to the objective facts about their country. Patriotism also insists that one's country is better than everyone else's, and it leads to all sorts of nastiness like wars. Patriotism over one's religion is no different. It is easy to turn a blind eye to the darker side of one's beliefs, to the assumptions that must co-exist with your established beliefs, but which no Sunday School teacher really spends any time on. Consider Nazi Germany for a minute. Almost everyone, except for a few punk skinheads, will agree that Hitler was the embodiment of evil, that his Third Reich was a ruthless and evil empire. Yet, it would not be hard to imagine a poor German in the 1930s and early 1940s being quite in awe of Hitler. It would not be hard to imagine a German peasant praising him for re-igniting the German economy into a world power, for re-claiming the German territories that were unfairly taken from them at the Treaty of Versailles after World War I. Hitler brought in autobahns, Volkswagen, and gave people jobs (the all important mantra of today's politicians). You might even say he was Germany's saviour. Yet, his evil deeds cannot be ignored or glossed over. All the good he did for Germany came at a terrible cost to the rest of humanity. Similarly with the Christian god Yahweh. He does so much good for Christians, offering them love, hope, forgiveness, and jobs, and yet punishes the rest of humanity eternally. No Nazi concentration camp could come close to the horrors of the Christian hell.
But I digress. The point of this post is not to compare Hitler and God. God wins that comparison hands down. No, rather I am trying to point out how ridiculous the notion is that God made humans. God is so human in character and temperament that he really offers nothing that humans cannot offer. He is fickle, jealous, unforgiving, and ruthless. He is also capable of great love, friendship, forgiveness and hope. What could be more human? We are all capable for such good and such bad. God is definitely made in man's image, both good and bad.
Another thought that must be examined, if you believe that God created humans with the intention of relating to them, of having humans come to know him fully and entering into an eternal relationship. One must consider his communication with humanity. Apart from those momentous occasions in the Old Testament when God actually spoke out loud, appeared as a pillar of fire or a burning bush, or walked about as a human being for a few years in the time of the Romans, God's only realy communication with humanity is through his book, the Bible. So, how effective of a book is the Bible, considering it is authored by an omniscient, omnipotent creator of the universe? How effective is it at helping humans get to know God and come to love him and want to relate to him? What would you write in a book if you wanted your human children to have a long-lasting and loving relationship with you?
Well, I'm pretty sure it wouldn't be the Bible. Imagine you were having a child of your own. You knew you wouldn't be around physically to guide and teach your child as they grow up, so you write a book for them to read, to help them learn about the nature of the world, about your character, and about how much you love them and want to relate to them. Would you spend the first two thirds of the book basically outlining your personal history, complete with all your vindictive little stories about how you screwed over everyone who ever crossed you or made you mad? Would you spell out in intimate details all the little rules that you want your child to follow, including how they should cut their hair and precisely what foods they should and shouldn't eat? Would you point out what a worthless piece of shit they are, and how their whole life is full of evil deeds and sin, and how the only way to really make it up is to try to spend the rest of their lives finding you and asking for forgiveness for being born? Would you pour a huge guilt trip over them, all about how you sacrificed so much for them so that they could have a life, how you basically gave up your life completely just so that they could have a life? How do you think that would go over it you wrote a book like that to your child? Just a hunch, but I don't think once they reached adulthood they'd be setting out on a mission to find you and spend the rest of their lives relating to you (when "relating to you" actually means begging forgiveness on a regular basis and having hope that you'll still forgive and love them, because you did include that part in your book to them as well).
So, the more realistic examination of what kind of person God is really doesn't leave much doubt that he's a human-created phenomenon. There is no god. God is a concept we created in the infancy of our history as a species to help us deal with our fear of the dark, of the unexplained, and of death.