BSG - the final season
POSSIBLE SPOILERS AHEAD, DONT READ!
Regardless of whether the original Cylons retained a memory of what happened that lead to guilt or if yet another unknown set of beings compelled them to do it - they are reliving what happened by reenacting it - creating a set of humanlike models, have those models populate a world, start a war with them, destroy all humanlike models but let a few escape. The escapes settle another star system, and the cycle repeats.
It would explain why XXX committed suicide: she found out that she was a Cylon by finding a medallion on Earth that showed her; it would explain why XXX can find her own dead body on Earth, and why there appear to be so many models.
Brilliant. I have no idea if this is what the series is headed for, but this would be what I'd consider the final stroke of perfection in what is the best example of recycling cultural garbage to create a compelling storytelling experience demonstrating what TV can accomplish.