The most clear proof for a creator is the creation. Since the world exists, it had to have been created. The difference between creationists and atheists is really whether the creator of the world was the world itself, or if there is another being responcible for the world's existence. Creationists would say that it is not possible for something physical to create itself. Atheists will say that since the concept of G-d is proven to be not comprehendable to humans, the world must have created itself. Also, even if an atheist will believe that the world is so great that it can actually create itself, and force itself into existence, he will not be able to agree that this world will have a will, and actually command people how to live their lives. This is my view of things as a creationist.
The evidence for the Big Bang is one bit of evidence that the universe was created. The only question is: What caused the Big Bang? The stuff itself (stuff = matter, energy, force, space, time or all of the above), or something else.
How is not the question. The point is that it has happened. The universe was simple at one point in time, namely the very beginning of time. The idea of simple is that it does not have to be created. By definition it is the simplest thing in existence and it requires no creating.