The Genesis system of creation is outlined in the first two chapters of the bible. The gist of it is that God created the universe in 6 days, starting on day 1 by creating light and darkness. On day 2, God proceeds to create the heaven, saying "Let there be an expanse...." He then divides the waters that were above this expanse from the waters below it, and calls this new expanse "Heaven." Day 3 sees the creation of dry land and sea. On the fourth day, God lights up the heavens. Day five has brand new sea creatures and birds unveiled. On the 6th, final day, land animals and human beings are created. I'm an Atheist, so naturally, I feel obligated to point out the flaws in this Hypothesis. I can't even call it a theory, because theories are supported by scientific evidence. The YEC (Young Earth Creationism) hypothesis has very little scientific basis. What is scientific is highly questionable.
So if this almighty being can do whatever the hell he wants (he has unlimited power, yes?), why does it take six days to create the universe? It seems to me that it could be done in a matter of seconds by an almighty being. A simple "BANG!" and a wave of God's finger should suffice.
Of course, this all happened 6,000-10,000 years ago, and all the land animals were created at the same time. By this logic, humans and dinosaurs lived together, so why do all the dinosaur bones appear to be so goddamn much older than ours? I've asked this question to a few Christians, who promptly reply "God is testing our faith." Do they really believe that? Why would a god judge humans based on a befief for which no evidence was supplied, and in fact, much evidence contradicted? Thats not a test at all of moral quality or heaven-worthiness. If you believe in YEC, the Paleontoligist field of science would like to have a word with you.
As a Christian, you believe that god has existed forever and created the universe. As an Atheist, I believe that matter has always existed, and that the universe simply always was. You tell me "something had to create the universe," to which I reply without hesitance that "If something had to create the universe, didn't something have to create God? " Double standards, my friend, double standards. To the people I've asked, their response to that is "So why would you believe that matter has existed forever instead of god?" My answer is quite final. "I see matter here. I see no god."
A final point that Christians in particular seem to deny is the Theory of Evolution. Notice the word "theory." I used it because the Theory of Evolution has scientific evidence to support it. Many Christians believe that all species are exactly as God created them. Once again, Paleontology would like a word with you. Ya know all those bones from thousands of years ago that look like ours? I believe "she" was named Lucy. Her bones seem a bit similar to ours, but so much older... its almost like we humans descended from a species like Lucy! Oh, my bad, that just God testing your faith again.
You know what faith means? Belief not based on proof, evidence, or fact. You know why I believe in evolution? Fact, and strong evidence support it. Creationism has a 2,000 year old book to support it, a book of questionable dependability at best.
As Stephen Henry Roberts, "I contend that we are both Atheists. I simply believe in one fewer god than you. Once you understand why you reject all the other gods, you will understand why I reject yours."