Cylons were created by humanity. They evolved and developed a plan. What was this plan? Even now with the series finished, this question has not been answered completely. A sexy cylon in Baltar's head seduces him with hints at what the plan entails, implying that humans have strayed from belief in the One True God. Through apocalyptic measures, created wishes to put creator back on the path of righteousness... if any are left by the time they are done.
President Roslin is on a mystic journey when we first meet her, concluding that pragmatism wins over spiritual promise. She retains awe and wonder in the face of an inscrutable cosmos, but without the visionary aspect. Arguably she passes from one pagan philosophy to another. There is a clear connection between her and the cylons, the nature of which is undefined -have the cylons failed? A strong woman of conviction is no less convicted when we last see her. What exactly it is that commands her spirit is left open to interpretation, never definitely rooted in the One True God cylons espouse; in this respect, she is a failed experiment and human, all too human.
Gaius Baltar undergoes a very different transformation. He is convinced of God's perfection and beauty, proclaiming it to all and sundry. Knowing what we do about his character, the depth of his conversion remains unanswered. Without question he comes to his prophetic hysteria having endured experiences devastating to lesser folk, and provides the series' dynamic of how we come to recognize what it is we truly believe.
Is Baltar a cylon success story? He is like Paul of Tarsus, born a persecutor and reborn in fire, blindness and long wandering to become God's man.
All of this to say, Battlestar Galactica undertakes a great storytelling challenge: to tell of spiritual renewal without lapsing into cliche and preordained outcomes. As the series progresses, it is never certain where Roslin or Baltar will end up. When we see them at the end, it is a marvel. How amazing, too, that it unfolds within the trappings of a science fiction television show.