I didn't know about religions until I entered junior high where there was a "human culture" class. Before that, I was only pretty familiar with Greek mythology because it's very intriguing. I knew a little about "Adam and Eve", didn't know which category they belonged to, and I knew there was a guy named Jesus in a book named Bible, and another famous guy named Muhammad in Quran. That's about it.
Ironically, I read the "expurgated" bible (the first half of the Old Testament), without kinky sex and bloody violence (so basically 90% of the Bible was "expurgated", I can hardly call it "Bible" any more), the New Testament was too boring so I didn't read it. As for the Quran, I found the first chapter was almost exactly like the Bible, So I didn't read it either. Now I'm 24 and still find them boring.
Probably because I knew about religions too late, I couldn't and can't understand why so many people are crazy about them. Is it because they (including you) were indoctrinated too early, they were too young to say no, and they have only eyes for their "first class", like the new born cubs recognize their mothers by the very first sniff?
Also, I was wondering the possible origins of religions besides of my text book:
I won't be able to give an answer that you will accept, mostly because you think you have all the answers.
But no, religious beliefs are not something that only is instilled at a young age. I know people who have become religious in their old age. I know a large number of people who were brought up in a religious home, but who turned against religion as they became older. The mistake you are making is assuming that everyone views the world as you do. Since you had no religious teaching when young and find religion "boring" when older, you just assume that happens to everyone in the same situation.
Another mistake is your assumption that all religions are the creation of man. I'll grant you that a number are, but it doesn't follow that all of them are man-made. Nor is your statement that people in the middle east prefer monotheistic religions. History shows that the dominate religious beliefs in that region were polytheistic. The Old Testament of the Bible is filled with information showing the Israel was constantly being led into polytheism by the nations around it. A number of these gods are mentioned in the Bible (see Mythology, False Gods, and Their Worship for more details).
While you have rejected Christianity, you have done so from the position of ignorance. You haven't learned what it has to offer; you read only a watered down, abbreviate version of the Bible; and yet from that position of ignorance you find yourself superior to people who have read the Bible and follow its teachings. Now tell me, who looks more foolish?
But, just in case you are curious, different parts of the Bible are written in different styles. You strike me as a person how doesn't like historical records, so it is little wonder that you found the early books of the Bible, which are historical records, to be boring. But if you want to see what other parts of the Bible are like, find a New International Version Bible. It is not the most accurate translation, but it is a very readable one. Find the book of Esther in the Old Testament and read it. Understand that it is an historical account of something that happened almost 3,000 years ago. Next try the book of James in the New Testament. It is a plainly written book about morality and ethics with strong emphasis on practical applications to a person's life. Below are two examples of Hebrew poetry.
The fool says in his heart, "There is no God." They are corrupt, their deeds are vile; there is no one who does good. The LORD looks down from heaven on the sons of men to see if there are any who understand, any who seek God. All have turned aside, they have together become corrupt; there is no one who does good, not even one. Will evildoers never learn-- those who devour my people as men eat bread and who do not call on the LORD? There they are, overwhelmed with dread, for God is present in the company of the righteous. You evildoers frustrate the plans of the poor, but the LORD is their refuge. Oh, that salvation for Israel would come out of Zion! When the LORD restores the fortunes of his people, let Jacob rejoice and Israel be glad! (Psalms 14:1-7 NIV)
The heavens declare the glory of God; the skies proclaim the work of his hands. Day after day they pour forth speech; night after night they display knowledge. There is no speech or language where their voice is not heard. Their voice goes out into all the earth, their words to the ends of the world. In the heavens he has pitched a tent for the sun, which is like a bridegroom coming forth from his pavilion, like a champion rejoicing to run his course. It rises at one end of the heavens and makes its circuit to the other; nothing is hidden from its heat.
The law of the LORD is perfect, reviving the soul.
The statutes of the LORD are trustworthy, making wise the simple.
The precepts of the LORD are right, giving joy to the heart.
The commands of the LORD are radiant, giving light to the eyes.
The fear of the LORD is pure, enduring forever.
The ordinances of the LORD are sure and altogether righteous.
They are more precious than gold, than much pure gold; they are sweeter than honey, than honey from the comb. By them is your servant warned; in keeping them there is great reward. Who can discern his errors? Forgive my hidden faults. Keep your servant also from willful sins; may they not rule over me. Then will I be blameless, innocent of great transgression. May the words of my mouth and the meditation of my heart be pleasing in your sight, O LORD, my Rock and my Redeemer. (Psalms 19:1-14 NIV)