Dungeons & Dragons
Scooby Doo
Voltron
The scary thing about Thundercats is that I caught a couple of episodes last year on the Teletoon Network and I was shocked at how developed the scripts were. They had story arcs between episodes, character development of villains that stretched over multiple non-sequential episodes, and an overall plot that I had absolutely no recollection of from back in the day. In an era when cartoons were basically one-shot throwaways where nothing in any given episode affected the next, Thundercats was more like a soap opera (albeit a very adolescent version).