I see another reason why God must have been created by the human mind. The emotional and physical duress that some humans experience in their lifetime is so horrible that the idea of God as an everlasting, sustaining force—a friend that sticks by closer than a brother—is something powerfully satisfying and calming; a cure or antidote for life’s constant imbalance.
Also, the idea that Jesus was convicted and killed despite his innocence resonates with many who have been wrongfully accused, sent to prison or jailed, when they are actually innocent of the crime. One of the most painful feelings to have in life is to be accused of something when you know you’re innocent—yet no one else believes you. You become ENTIRELY alone. You might as well be dead. It is worse though, because you have to live with this knowledge and understanding. To have a deity affected by a similar circumstance? Well, that means he's traveled in our shoes and can understand our most trenchant pains.
When you think of the number of people in your personal life that you have been willing to interact with and give the time of day to—yet who are willing to give up on you after a certain point… when you think upon all of life’s tumultuous moments, almost dying of a disease or being currently plagued by one, perhaps a loved one is battling a disease…when you reflect upon all of life’s pain, break-ups and divorces, being ripped apart and insulted for every quark of your person on a literally daily basis, all the mistakes made, all the times your honest intentions have been misrepresented and misinterpreted, friends of old have turned against you—perhaps your mind needs to fabricate a succor.
Alas, we see the creation of a force that is forever unchanging, always there for you—a presence who cares for you. Whilst the rejection from old friends or relatives and the death of loved ones, you still have God. You still have someone who knows your situation and understands what you are going through and is there by your side. This person will always love you.
It is as if you created a copy of yourself in your mind that can identify with you in every way—someone who will always be there for you. Religion only adds more structure (i.e. doctrines) to this nebulous human desire.