As a deist, I do believe that a supreme being created the universe. My belief in God is one that appeals to my intuition but, by no means, can I make the assertion that this is the simplest and most logical explanation for nature. Most atheists don't claim to know there is no conventional God, only to doubt the existence of such a being based on the lack of evidence for it. Sure, I do know some atheists who think that there may be a single entity behind all things in nature but the difference between myself and them is that I, and most theists, go one step further in our faith that said entity is actually a thinking being.
It's unfair to presume all atheists share the belief that universe (or multi-verse, for those who think there are more than one) has always existed. The prevailing opinion of the scientific community, comprised mostly of atheists, is that the Big Bang is the most likely explanation for the universe although there is a relatively new theory that suggests a cyclic universe.
Even if there were some scientific way to prove that a supreme-creator being is at the heart of the universe, most atheists would be more likely to become deists, like myself, than followers of the prophets since there is no evidence supporting the supernatural claims of scripture.