Toth died while sitting at his drawing table at his home in Burbank on May 27, his son Eric said. He was 77.
Eric Toth said the cause of death had not yet been determined, but his father had been in failing health for years.
Before working in animation, Toth was a comic book artist, widely regarded as brilliant, who had some success but even more frustration.
He rarely held on to an artist job for long because of a simple, subtle drawing style and a stubborn adherence to his artistic principles. And he preferred pirate tales and westerns to the more popular super hero comics.
"Toth was one of the most brilliant artists ever in comic books but also someone who was the odd man out in many ways," said comics publisher and critic Gary Groth. "He was never associated with a particular character, and he was pushed off to marginal titles."
But Toth's forms would prove influential in underground comics and graphic novels in later decades. Comic artist Will Eisner called him "a mastery of realism within a stunning illustrative style."
Toth was born in New York, where he lived and worked until settling in San Jose in the late 1950s. While living there he worked for Dell Comics on titles derived from television shows like "Sea Hunt" and "Zorro." That led to animation work in Southern California, where he moved in 1964.
Drawing for Hanna Barbera in the 1960s and 1970s, Toth designed characters for adventure cartoons "Jonny Quest" and "The Herculoids" in addition to "The Superfriends" and "Space Ghost," and he achieved the wider recognition and commercial success that had eluded him.
"The work he did there touched more lives than anything else he had done," said Paul Levitz, president and publisher of DC Comics. "He found ways to take characters like Superman from their more complicated printed form into a simpler form for animation that still held on to their power and majesty."
Toth is survived by sons Eric and Damon Toth, daughters Dana Palmer and Carrie Morash, and four grandchildren.
At Alex Toth's request, no memorial service was planned.