If I said I was a deity, I would be judged to be insane or at the very least deluded. If on the other hand I said I believed in a deity, I'd belong to a very large group of followers of a religion.
The credibility gap seems to concern the distance from the evidence and the demands made. If an individual of our acquaintance claimed to be a deity, we would expect them to have supernatural powers, omniscience, and other characteristics we know from experience to be impossible for humans. So we rule out the possibility that they could be a deity, and regard them as dishonest, insane, or at least deluded.
So as long as the idea of a god is out of reach of evidence, separated from the world of consequences where such a claim could be challenged, it can remain apparently credible. Any demand for evidence is dismissed by the definition of a god - a god is ineffable, omniscient, ever-present, invisible, etc. For the world of everyday reality, gods cannot be shown to exist because there can be no tangible consequence. For many that's enough to rule them out.
So to provide justification for belief, there has to be some indication which will attract and convince believers. So an appeal is made to explain the origin of some mysterious aspect of human lives. Typically this involves quasi-mystical concepts like "the good", "evil", "truth" and so on. Since such concepts cannot be explained on a factual basis (they refer to intangible concepts or at best are simply adjectives), they are placed in an appropriately abstract state - ready for an equally abstract untestable explanation.
Now this abstract space that religion occupies is full of controversy. Since nothing can be demonstrated, everything can be challenged and churches, though united in their main aims (perpetuation and growth), can only appeal to equally abstract ineffable causes.
In much the same way as philosophers have entertained themselves discussing the nature of reality without arriving at anything approaching a consensus, religious discussion has as a sole purpose (soul purpose?), the perpetuation of the focus on the question in dispute. Making the question of "good" and "evil" into a difficult question, lends apparent profundity to the question.
In fact, terms like "good" and "evil" are adjectives used to express a comparison with our own values. We judge things to be good or evil in comparison to values we support. There is nothing in reality that corresponds to the good, or the evil. It's a false profundity.
Unfortunately, theological discussion and its philosophical equivalents provide career paths for those perpetuating the confusion. But a moment's clear thinking shows the absurdity. Given that there is some deity, how is its nature discovered in such a way that we can distinguish between support for Zeus, or Odin, or Allah, or Jahweh, or any of the thousands of others? And if all are equivalent, we are reducing religion to a psychological and social phenomenon. That's why religions fiercely defend their differences. But there is no strictly philosophical basis for ruling out any of them if any of the others are included.
On the individual level, how can someone distinguish between what they call a religious experience, and an intense emotional one? It can only be through the way they are predisposed to describe them. And how can such a description be distinguished from delusion? Unfortunately, it can't.
It's only the social acceptability of religious statements which avoids religious individuals being considered as delusional. Society accepts religious statements as non-delusional whereas psychologically equivalent statements which talk about supernatural beings would be considered medically significant, and the individuals would be given some form of treatment.
For the religious, their forms of thinking, providing they are mild, doubtless have psychological benefits. But those benefits apply equally to other beliefs in imaginary beings. A child takes comfort from the presence of an imaginary friend - the comfort is no less real for the fact that the friend is imaginary.
But equally, reliance on emotionally perceived messages from deities, imaginary friends, or other delusional objects, can have serious consequences. While the messages from god accord with normal social values, we say that people are "good". When they don't, we lose no time in diagnosing the patients as schizophrenic. When they are muslim suicide bombers, we call them terrorists. When it's someone like George Bush who claimed to have a hotline to God, millions of Americans took him seriously and Iraqis are still suffering the consequences.
The belief that some religious people have that the deity is what keeps them moral is perhaps the most worrying aspect of religion. If an insubstantial super-being is required to keep them in tune with accepted social values (which we call morality), then their behaviour is on very shaky ground indeed. Far better that they lose the mystical and engage honestly with the values of society that they support, and dispute those they disagree with. At least they, and everyone else, will know where they stand.
