no intelligent person is religious. Religion is only reserved for stupid ignorant proles. To believe in an invisible man that watches over you and listens to your prayers is the height of stupidity. What you are instead noticing is the phenomenon of intelligent people lying. Many will lie and say they believe in god, whether it to be able to fit in with society, or not disappoint their parents, or because they want to take advantage of other peoples weakness of stupid beliefs in order to curry favor and gain trust/a personal relationship with another human being. In their heart of hearts however, if you were to lock them in a room and hook them up to a truth ray, you would see that there is no such thing as an intelligent religious person.
I actually agree with part of what you said. People who believe in an invisible man who watches over you, are stupid. The problem is, most religious people don't believe in an invisible man, and that's not what they pray to. You are under a false and rather childlike understanding of what God is, and apparently, you are incapable of comprehending God in any other way but as a physical entity or being. I don't know of anyone who believes in a physical being they define as God. Such an entity can't exist, it defies all logic.
However, if you can manage to expand your mind a bit, and think outside of the physical realm you are comfortable with, you realize the universe around us has order and organization. The miraculous life that surrounds us is meticulously complex and interdependent, the chemistry and physics are predictable, nothing is random. The possibility this all happened by pure chance, is very slim. This leaves the possibility it happened because of some divine intervention we don't understand, a very realistic consideration. Not an invisible man, but something not of the physical realm we are aware of.
When you consider the amount of knowledge man possesses, is far less than the knowledge yet to be gained, nothing can be dismissed from possibility. To do so, is arrogant, simple-minded, and foolishly stupid. There are tens of trillions of stars in the known universe, each most likely has a body of planets orbiting around them, and when you consider the material which makes up life on our planet is relatively common in the universe, the likelihood life exists elsewhere, is overwhelming. Perhaps the knowledge of what is responsible for our universe is known elsewhere, by other older and wiser forms of life? To argue that is not a possibility, is to close your mind and maintain ignorance.
One intriguing aspect to humanity which has always been of curiosity to me, is the profound connection mankind has always had to spiritual beliefs and faith. Now, many non-believers will discount this by explaining it away... it's simply mankind's way of dealing with what he doesn't understand. But... other living creatures lack understanding of things, they don't have a need to create a behavior to cope with that. If you were scientifically studying any form of life we know of, observing the behaviors of the species, to discover a unique attribute not found in other species of the same family, you have to conclude there is a fundamental reason for that behavior, it is somehow important to that species, and plays some role in the nature of the species itself. If you discover other distinctively unique attributes, you might make the rational assumption the attribute and behavior are co-related. With humans, we possess a unique attribute best defined as "humanity." It is the distinction which separates us from our cousins the chimpanzee and other similar primates. Is is coincidence that humans also possess the behavior of spiritual belief? If this were any other species, we would certainly conclude the two are somehow related to one another, there is some connection.
No one can force you to believe in God, and no one can "prove" God to you. And if you have closed your mind to any possibility that something outside the physical realm might exist, that you simply can't comprehend, that is entirely up to you. I can almost guarantee you that God is not a man, invisible or otherwise, and has no physical traits. My personal belief doesn't facilitate prayer to God, because I don't believe God has human attributes, it doesn't "care" if you are "good" or "bad" and it doesn't have a need to be worshiped or loved. I realize a great many people don't agree with my view of God, and I am fine with that. I am not 100% sure of what God is, maybe they are right and I am wrong. I just know what I know... I don't "believe" in God, I personally know and understand the spiritual guiding force of the universe, I have felt it, I have experienced its presence. For someone to try and tell me that doesn't exist, is like me telling you that your own mother doesn't exist.