Supposedly Julius Caesar was worried about this same thing. When he was around 30 he came upon a statue of Alexander, who at his age had conquered the known world. Caesar had very little to show for himself at that point.
He was in his late thirties and early forties before he had any remarkable success or power.
Success isn't measured in critical acclaim. He was in many popular movies including some blockbusters like Jurrassic Park and was quite successful long before Pulp Fiction. Pulp Fiction was far more notable for reviving John Travolta's career than doing anything for Sam Jackson.
If Jackson himself measured success in the amount of supporting roles he could land, then sure he was "successful" prior to Pulp Fiction. Surely you'd agree that he didn't play in any noteworthy lead roles until AFTER Pulp Fiction...
Ray Kroc's book Grinding It Out is a fantastic account of his work creating McDonalds. He definitely did his best work later in life, and proof that you can make your mark at any point in your life. It's a great read.
Frank Lloyd Wright, though successful early in his life, had all kinds of rises and falls in his career. He's also a terrific story about Renaissance in your own life.
Reagan was elected as a two term president and remains one of the more popular presidents in recent history.
Reasonable people may respectfully disagree about whether or not he was a good president and whether or not he took the country in the right direction, but I think anyone saying he was not a successful person is using a very different definition of "success" than the common meaning.
Yeah, It wasn't the unsustainable economic, political, social and environmental system that was Soviet totalitarianism. It wasn't the thousands of political dissidents in Easten Europe who were active, organizing and being persecuted before Reagan was even elected.
No, it was all because your Actor-President gave a nice speech and ran a deficit.
(If I was American I'd probably vote for Democrats most of the time, but it's funny how users seem to know exactly what did or didn't cause the fall of the Eastern Bloc)
Rodney Dangerfield started writing jokes when he was 15. He finally hit it big when he was 52.
Ray Kroc was 52 when he started McDonalds.
Orville Redenbacher was 58 when he founded his popcorn business.
Ronald Reagan was a B-List actor who was 56 when he became Governor of California and 70 when he became President of the United States.
Grandma Moses was 78 when she started painting.
Tina Turner was 44 when she recorded her first #1 hit.