Which show was the most financially successful and longest-running animated series until The Simpsons?

The Flintstones holds the distinction of being the most financially successful and longest-running animated series before The Simpsons. Premiering in 1960, it was not only a pioneering show for prime-time animation but also achieved remarkable commercial success through its relatable family dynamics and clever satire of modern suburban life. The series garnered a massive audience, leading to a significant cultural impact and extensive merchandise sales, which contributed to its financial success. The Flintstones set a precedent for future animated shows aimed at adult audiences, paving the way for series like The Simpsons while maintaining a record for longevity at that time. This combination of factors solidified its legacy as a cornerstone in the history of animated television.