the whole religious/prophecy subplot/angle in Battlestar Galactica was probably the most painful thing I'd ever seen. I know what it means basically (at least I think I do) - that the events leading up to the destruction of the 12 colonies was unavoidable, and that history repeats itself again and again, leading to myth that seems very familiar to their modern times... but every time the series took a turn towards the super-natural, I cringed. I couldn't stand it.
On the other hand, I *loved* the cylons. Once I gathered what their deal was (the series takes about 2.5 seasons before it really capitalizes on them and reveals their side of things/way of thinking), I found I could predict them because they were written in a very.. consistent way. Model Number 1 describes in passing about how during a battle, he was injured, and casually found a piece of jagged metal to cut his own throat with so that he would ressurect in their ressurection pods. That was a very profound moment. The Cylons really were machines, they thought like machines, they acted in ways like machines, and were COMPLETELY not expecting individual personalities to arise out of individual units through their interactions with the humans, but they did, and seeing how that effected their society was so interesting to me.
And then along the line somewhere, the president would have a lucid dream about some prophetic thing and I would fall asleep completely. One show contained both the most compelling bit of... society writing? Like character building but on a grand scale?.. I'd ever seen, and also the LEAST compelling bits of writing I'd ever seen.
The only thing more underwhelming in terms of writing was the wet fart that was the Lost Series Finale. Even after you understand it (and I don't think anyone "got it" the first time they saw it), it still leaves you feeling completely empty.
So... The Series Finale of Lost.