This is an argument from authority, and does not mean that a god(s) exists, no matter how many believe it. The number of people who have "faith" in some god, just means that people want to believe in something. It does not mean that what they believe in is real. "All of the world's religions can not be right, but they can all be wrong." - Matt Dillahunty
Not an argument from authority at all. Or even numbers. Just common sense. Certanly numbers or the prevailing wisdom is not authority. Most of the world once thought the Earth to be flat and that it was the center of the universe. We now know that despite how much peer review there was, that was wrong. But also, that was not based on experience, but rather peer teaching.
But when an extraordinary number of persons report a personal experience, and no conspiracy is possible, it is only logical to conclude that they are experiencing something whether they understand it correctly or not. If you have never been in love, do you conclude that no such thing isn't possible even after many, many others report the experience of being in love? Do you say it is only a belief?
To address the rest of your post:
Personal experience, is not and never will be empirical evidence about an objective phenomenon, no matter how many people experience it, simply because there are other possible explanations. I could make the argument that this phenomenon is the result of humans' need to believe in something to quell the fear of death and fear of unknown, which are two fears that make us feel out of control, thus producing anxiety and suffering. If a belief in god will quell this anxiety, it doesn't matter whether it is true or not, it only matters that it produces the desired effect of putting us at ease. This is the problem with the human mind. We will believe things just to feel better about ourselves or the universe, whether or not it corresponds with actual reality. So really, this is a psychological issue. In all likelihood, this is exactly why humans are primed to be religious. We have never had a natural explanation of anything until only very recently in our evolutionary history. Therefore, storytelling and religious ideas have been central to our understanding of the universe and our place in it, and thus, our understanding of ourselves. Psychologically, the ability to place our selves in the universe with a cohesive model that makes logical sense, is very important for our emotional well-being. Science can now provide that model on natural explanations. God is no longer needed. Those that hang onto god, are merely expressing an outdated version of our human software. It's time to catch up, and update.
The point is, is that there are other possible explanations for why so many people believe in god, other than god, and they make just as much, if not more sense, than "god exists."