Oddly put, but your response is essentially the correct refutation of the argument that since everything must have a cause, there must be a God, else, where did the universe come from? Even if the "big-bang" is granted, it just pushes the question back to, alright then, where did the "bib-bang" come from? But if the answer is God, then God must have a cause, because, if God does have a cause, then the premise of the argument, that everything must have a cause, is denied.
But, this does not mean there is no God, or that there is not good evidence for God.
Dostoevsky asked a very interesting question in Notes from Underground. "What is the ultimate reason for existing?" We exist, without a choice, but to continue to exist does require a choice. But ultimately, even if you choose to continue to exist, that choice will be thwarted.
It's like this. What's the point? There can be no objective in choosing not to live. That's the end of all objective. But if you choose to live, at best, you can only be successful temporarily, and then you die and you will have failed to fulfill your choice.
If God exists, there could be a point. That does not mean God exists. But if God does not exist, there is no point, and how does a pointless existense come to be?
Hank
Part of the problem with this discussion is definitions. The way most people view causality in the universe is pretty simple and based in the classical physical universe that we observe every day. However, the REAL scientific definitions get very weird because they have to deal with mathematics and conditions that add new degrees of freedom to causality that are really beyond the average human experience, though easily measurable in a good laboratory.
Many of the conservation and causality laws that we all learned in basic physics are actually "white lies"; they aren't really true and are adaptations of the real mathematics with all the strange stuff removed. To a certain extent this makes sense, as it makes it much easier to learn a practical approximation that is perfectly applicable for what most people would use it for. Only physicists and the occasional engineer have to burden themselves with the real equations.