6. Dinosaurs
One of the biggest issues that can really sink a series finale is when a great comedy decides to end its run on an unnecessarily bleak note. Take, for example, Dinosaurs. You know, the lovable show about the working class family of dinosaurs that was pretty much Roseanne meets The Flintstones? Well, Dinosaurs had its share of dark humor. One of my favorite episodes was the one where the grandma went to her 60th high school reunion and she was the only dinosaur left. Classic. But I don't think anything prepared me for the final episode, when Earl realizes that he has destroyed the environment and caused the extinction of his species. So the Dinosaur family sit in their house, awaiting the cold and inevitable grip of death, as snow begins to fall. Roll credits.
How It Should Have Ended... I think that they could have addressed the impending doom of the dinosaurs in a less overt way. Maybe they could have had the dinosaurs cheerfully oblivious to all the changes that were happening in their world. The episode falls apart when the dinosaurs are coming to terms with their extinction, because it just feels so incredibly dark.