Episodic shows are good for ensemble stories where none of the characters is going to change much over time. Serial shows are good for a story that progresses across there series. The stories that can be told with each type are almost disjoint. The original Star Trek worked as an episodic setup. Voyage didn't. Stargate: SG1 was mostly episodic and mostly worked as such. There are lots of episodes that could be slapped into any season without damaging either the episode or the surrounding season.