The Fantastic Four animated series debuted on the same day as the 1967 Spider-Man series, though the Four didn't survive for quite as long, lasting just 20 episodes.
One thing this series got right that a subsequent series did not was the lineup of the team. Mr. Fantastic, the Invisible Girl, the Thing, and the Human Torch were all here to battle it out with classic villains such as the Mole Man, the Skrulls, and of course Dr. Doom.
The series also told the epic tale of the coming of Galactus which also introduced the Silver Surfer. This arguably best know Fantastic Four story would be retold in the 90's animated series and in the live action sequel film.
Unfortunately, a catchy theme song is not one of the things that this series will be remembered for.