Another franchise killer is Ronald Moore and his pet dufus, David Eick, (who, himself, killed The Bionic Woman franchise in record time), the Berman clone (clown?) and protege', but that "story" belongs in another forum entirely.
You are certainly entitled to your opinion about nuBSG, many people don't like the direction it took, but to call Ron Moore and David Eick franchise killers is incorrect. They took a franchise that had been dead for over 20 years, a franchise that few fans even wanted revived (I personally thought it was a terrible idea) and they made it into an international success. It became Sci-Fi channel's hottest property. They chose to end it after season 4, they are going to be doing several TV movies after the show is off air, and they are going to be making a spin-off series based 40 years prior to the events of the show.
Hate Ron Moore and what he did all you want, but don't claim that he is a franchise killer when he successfully revived a franchise.
Plus, I don't think he gets along all that well with Rick Berman.
On topic, Enterprise couldn't continue past season four, it was losing the network too much money. I know they had offers from Sci-Fi and the like, but they wanted to keep complete control of the franchise so they could bring it back at some point. I wanted a pause for a few years after Voyager but they decided to keep going, and I wanted Enterprise to stay on air for seven seasons, but it was the right financial decision to make.