I still can't stop but think how stretched out the Hobbit films were, for an otherwise short book. That's a sin that stains forever with me. The Lord of the Rings films, do have their own flaws, but they're fairly contained and can be debated as to whether they were good or not. I have so much trouble excusing anything with the Hobbit though.
And I hope we never, ever see anyone tackle The Silmarillion. Simply because, there will be so much improvised fluff in that would-be film, that it'd make the Hobbit films blush.
I love/hated BSG ever since they expanded the number of Cylons for like the 3rd time. It was around that time it leaked that they didn't have any plan and Ron Moore had been lying to the fans for years.
After it was over he said, (paraphrased) "LOL, There was no plan. If someone suggested more hidden cylons and it sounded dramatic we would go with it and figure out what that would mean in the next writing session."