I'm an admirer of Carl Jung for the way he was able to systematize and objectify the human psyche through his studies of dreams and active fantasy. (Joseph Campbell took Dr. Jung's ideas further into the field of mythology.) Carl Jung stated unequivocally that we need a deity (Or deities) to become whole people. I will describe a case of his as an example: He had a female patient with a neurotic condition called a father complex. This complex involves an infantile attachment to one's real father. It will block the progression into adult relationships, as any potential male could never meet the perfect, idealized image of the father. During her analysis, the patient had a recurring dream of standing in a beautiful field with a warm, embracing wind, that gave her a feeling of bliss. Dr. Jung was at first perplexed by the dream's meaning. Through mythological research, he discovered primitive tribes that worshiped a wind god, which he termed Wotan. His patient was cured when Dr. Jung realized that her psyche was spontaneously producing the deity that she needed to become a whole person. He encouraged her to integrate this god into her life. By doing so, she was able to discard the infantile worship of her real father.
It is important to understand that in Jungian thought, the word god does not necessarily mean the Judeo-Christian God. According to Jung, the human psyche is always striving for wholeness. If one's psyche is unbalanced or blocked, the unconscious will produce material in an attempt to restore balance. An unbalanced psyche will result in a painful neuroses, or worse.
So my answer is yes. We need a deity to be healthy, whole people.