What you've just described is commonly referred to as the problem of causation. It does necessitate that some kind of greater force, some first cause, independent of the known universe must have existed in order for the universe to exist at all.
This is a good argument, actually. I agree that we can't really account for this, and so therefore some kind of something must have existed before or independently of the known universe.
The problem with theology is that right here is where the reasoning stops. We have no idea if this unknown force is a conscious entity, or just the sum of all natural forces, or any number of other things--in fact, we don't know anything about it, and therefore can't possibly attempt to assign any specific properties to it.
You are correct that anyone who claims he knows for certain that no such greater force of any kind exists or ever existed is fooling himself--it's obvious that he has no answer to the problem of causation.
But anyone who claims that he knows any specific properties of this vague greater force is also fooling himself, because there is no evidence for any of them and no way to obtain any. Whatever this vague greater force is--call it "God" if you really want to--it's a far a cry from most modern theistic conceptions of God, and that's why many people identify as atheists. Intelligent atheists don't claim to have any real knowledge about the origin of the universe or any solution to the problem of causation--they identify as atheists simply to signify that they don't buy into any of the specific theistic conceptions of "God" that are abundant in popular religion today.
I think it's quite possible to be an atheist and still not claim any answer to the problem of causation, because this "vague greater force" that we know nothing about and can't possibly hope to comprehend is not necessarily "God"--what are the properties of God? Most people who believe in God try to claim that they know specific properties about him, but that's clearly impossible.
Who says this vague greater force is actually God, anyway? It may not be omnipotent or omniscient or any of that stuff, but theists think that they know all about it. "God" by most people's definitions has all kinds of specific properties, and atheists identify ourselves in this way simply as a method of dismissing any conceptions of God as a conscious entity, or as something about which we can really know anything. We don't claim to know how the universe was created, and we don't have a good answer to the problem of causation--but these things don't necessitate the existence of so-called "God" by any modern popular definition.