Farkel, your deist argument is essentially the same as Aquinas' first three of his five ways, or the slightly reworded kalam cosmological argument. Both of these arguments are rife with logical problems. To paraphrase and combine essentially what the arguments are, they are essentially what you stated. Contingent things have to have a necessary cause, if the universe began (and the big bang says it did) then it had tohave had a cause, and this cause we call god.
One problem is that this assumes that an infinite sequence stretching forever backwards is nonsensical, followed by assuming a being that exists infinitily. It assumes the universe had to begin, it couldn't just exist infinitely. Even if the universe simply expands and contracts and the big bang was the expansion after the contraction, even if you accept that as a possibility, the argument suggests that stretching infinitely backwards cannot be true because it's nonsensical, there had to be a beginning at some point. But then it turns around and labels god as being infinite and having no beginning. It also provides no reason as to why there couldn't be an infinite regression of gods creating gods and eventually a god creates the universe, it is simply assumed that such infinite regressions makes no sense, and then suggesting that a single infinite being makes more sense. Some theologians tried to get around this by labeling everything in the universe as "contingent" which requires a "necessary" being, and that being we call god.
Even accepting the premise that everything is contingent (which quantum mechanics throws that notion under the bus, but just to assume for a second), and the universe itself is contingent, why is the necessary start to all contingent things an "agent"? Why does that require a human-esque intelligence that desires to create and design? Why couldn't this "necessity" simply be energy? Quantum mechanics once again shows that energy is always popping in and out of existence without "cause", energy is not strictly a "contingent being".
And that gets to the heart of the matter. None of the arguments that are made for god actually require a god, merely a beginning, and then they label the beginning god and claim that it is an intelligent agency, which is not a logical assumption, just a cultural assumption. And even the arguments requiring a beginning aren't particularly convincing because they argue that everything requires a beginning except for this special class of being that doesn't begin because we say so, and we need something to begin the other stuff that needs a beginning....which is not exactly the most parsimonious way to a universe.
Stephen Hawking is going to be on...I think the discovery channel sunday talking about the existence of god(s) in creating the universe. His position is that physics have progressed enough that god is redundant. On the sub atomic level particles are non contingent, they "bring themselves" into existence, or rather (so as not to anthropomorphise them), they exist without cause, and prior to the mass expansion in the big bang, the universe was sub atomic, thus the universe simply existing in a non contingent way does not contradict any physical laws.
The interesting question isn't "why is there a universe", the interesting question is "why do matter and energy behave the way they do?", and even in that field of understanding why the physical laws are the way they are, physicists have made great strides. Either way simply saying "we don't or can't know what existed before the big bang, so there must have been an intelligent super being (or beings) is neither logical nor necessary in understanding the universe or existence.
