The big bang theory is very good explanation for the "How" of the early universe, especially with new information about Inflation. Of course this isn't the Astrophysicists Corner (though they're perfectly welcome to enlighten us further on all the juicy, sciency details), so for our purposes lets think about the "Why" of the creation of the universe. Now before the big bang theory, there were two general ideas about how the universe came to be in its current state;

1) The universe is finite and was created by an eternal God / Yahweh / Allah / Brahman / gods / spirits / flying spaghetti monster / multidimensional alien / what have you.

2) The universe is infinite and eternal, having always existed and will always exist, and requires no supernatural power to create it.

Naturally the first idea is repugnant for scientists to accept, and was ridiculed for breaking the law of conservation of mass. The first theories answer for this is something along the lines of "dude, supernatural, as in does not obey the laws of nature yo!". Scientists refuse to accept this theory because it proposes something not scientifically observed, and when we get right down to it science is the art of detection and observation. Remember that, it becomes important later. After the big bang theory the second idea (infinite universe) is considered defunct, and now the "scientific" reason for the universe existing is...

3) The universe is finite and was created by a natural process. I. E. the universe happened because its natural that universes happen.

Well this presents a problem. Namely the conservation of mass (ah pesky conservation of mass, it would make everything simpler if it just didn't exist, unfortunately, that's not an option. Yet.), which states that matter can neither be created or destroyed (the same reason that idea number one was ridiculed. Now there's some bittersweet Irony.). The modern working theory now is that during the very earliest parts of the big bang the laws of the universe were not yet set, and therefore conservation of mass did not even exist, which allowed for matter to be created, with basically no cause.

Now the real question that these theories are asking can be put into the question "what caused the big bang?". It is here that our science, mighty though it is, finds its limit, where there can never be a telescope long enough, a sensor sensitive enough or a spaceship close enough to tell us what was before the universe. So now we get into the real philosophy, the purely mental task of thinking about what could create the universe. Astute readers will notice that the primary divergence point between the first and third theory is what caused the universe. For our purposes we're going to call the reason for the big bang, the Creation Cause (or CC because typing is hard and I'm getting distrac- ooh shiny...)

Theory 1) The CC is supernatural and sentient, meaning that it can decide to do something its never done before, and is self aware enough that it does not have to do it again.

Theory 3) The CC is a natural event, either recurring regularly, like, lets say monsoon season.

The problem with theory 3 is that if it recurs naturally, and is outside the universe then it should repeat ad infinitum, creating universe eternally, which means both into the past and the future. This would mean that our universe should have an infinite number of older sibling universes. Now the reason that scientists reject theory one is because it proposes an undetectable entity created the universe, and science is all about detecting. So the choice we are left with is an infinite number of undetectable universes, or a finite number of supernatural entities who can create a universe once and stop. Occam's razor states that when given two options the most succinct one is probably true. I see a single God creator as a more succinct option then an infinite undetectable universe spewing natural phenomenon. Therefore I propose that it is more rational to believe in a creator entity then it is to believe that the universe occurred naturally.

And with all of that said, if anyone cares enough about my ramblings to form a rational rebuttal, I invite you to do so, as long as you maintain the level of civility and politeness as we have thus far.

P. S. GE, thanks for taking the time to comment Aquinas and Anselm were great men and incredibly skilled at Apologetics, however their proofs, and my proof above are very subjective in my opinion, and I am trying to avoid having a "I say there's a God!" "Well I say there isn't!" *erupts into flame war* argument.