Every god of every religion exists. Why is that? Because people believe in them. Belief is something similar to currency amongst the gods, as it were, because if people believe in something, it becomes real. The more belief people have, the more concrete and 'real' that which they believe in becomes. The concept is called 'consensual reality'. This is not to say that if I believe that I can fly, I can jump off a building and fly. Quite the opposite will occur, I assure you. Now, the reason for this? The Consensus states otherwise. The Consensus is formed of the commonly accepted facets of reality, held close to people and nutured. Humanity has made realities of it's beliefs. An example of this would be the dollar bill- it's not worth anything but for the fact that people believe it has value. It is paper with ink on it. Now what kind of worth would that have without the belief that it actually has some? Very little. The United States is not even on the Gold Standard anymore- so it is not representing actual gold in a treasury somewhere (the value of gold could be subject to this, but at the moment, I shall only address the dollar bill). So the dollar bill only is worth a dollar because the government asserts that it is and we believe that it is. This concept is the same one that I apply to gods- they exist because people believe they do and they also believe that their gods are capable of doing things- and thusly, they become capable.
You offer a position but state no evidence for why it is true. Just because something can be true does not mean it is. Aliens could have built an invisible theme park on Mars, but there are no reasons for me to believe that this is the case.
Concerning the dollar bill example, first of all, ink and paper have no discernible inherent value; the statement that they have 'very little' is an assumption. Secondly, the value humans place on dollars is a social understanding of a representation of work and effects the way we interact with it and each other—it does not effect the inherent value of the paper and ink.
Here is where you confuse objective and subjective truths. Of course the reality of people's opinions or thoughts change when we think differently. Anything having to do with how a person responds, interacts, interprets, etc is subject to that person. Also, multiple people do not need to believe that I like ice cream for it to be true. Therefore subjective truths are subject to the individual that they belong to. Objective truths, like there is ice cream on the table, or God(s) exist(s), are not the type of thing that a person can believe into or out of existence without having the power to actually change them. For instance, it is true that before this point in time something existed. (That is because I know that something exists now, and because nothing cannot bring about something, there must have been something before now.) It is necessarily true. No amount of me or others believing that nothing existed will or can change that fact; it would be impossible for it not to be true. Therefore there are at least some objective truths that cannot be altered by a 'democratic reality.' The idea that a group could believe away the ice cream on the table would require a lot to prove it to be true.
Moreover, why do only humans have this ability? What about the omnipotent gods they created? If these gods really do exist like lots of people believe they do, why can't the gods also just stop believing in us? Or perhaps not believe that we can disbelieve them into oblivion? Or perhaps use their omnipotence to make us so we can't? If they really exist like humanity believes they do, then according to your view, they must be able to do that.
This view has unavoidably contradictory conclusions. The Christians (about 1/3 of the planets population) believe that there is only one God, that no others exist. Other religions, like paganism, believe in multiple gods. Are the Christians right because there are more of us? If so, you are wrong that there are many gods. There cannot be both many gods and only one God at the same time because these views are in direct contradiction with each other, including many other beliefs that people hold.
Popular opinion has been found to be wrong by the few. People used to think the Earth was in the center of the universe until Copernicus found that this could not be the case. If the majority's belief's manipulated reality, Copernicus should have been wrong. Or perhaps this never happened. Perhaps it is only a widely held modern belief that has caused it to be true. Then if it is true, the majority has still been incorrect about reality, and therefore their beliefs do not change it.
This argument is self-refuting. This type of argument is very unique. Most people have never heard of it let alone believe in it. Therefore if you are right, that reality does bend to the majority of people, then because the majority of people don't believe in it, it is not true.
Conclusion: you are wrong.