Well he did come back a few times and voice a few things over, like an animated movie and a James Bond video game, so it's not like he quit completely. It is unfortunate that he quit acting in front of the camera under similar circumstances as Gene Hackman, right after starring in a giant bomb.
There are some actors who do their best to end on a prestige piece (Warren Beatty/Robert Redford), others that leave after a terrible experience (Hackman etc), and then some who act in as many films as they can right up to the moment of death which leaves their final couple films as stains on their legacy (like Peter O'Toole). I guess it depends how their finances were and what they value. Laurence Olivier was well aware he was acting in a bunch of stinkers in the early 80's but said that he did so just for the money to leave to his children as he knew he would die soon. I guess you can't really fault him for that.
In defense of Lawrence Olivier, he WAS in "Clash of the Titans" and that movie made a really large profit and he was awesome in it. The acting really carried that movie (It's probably the best out of all of the Ray Harryhausen stop motion sword and sorcery films).
After he died, he was mostly remembered (by the younger generation) for that movie. So, even though he did four movies that all bombed after that (one was with Mel Gibson and Anthony Hopkins!) he did seem to end on a pretty (although deceptively) high note.
Yeah, so did I. It was the end of an era for those types of special effects. It's sad because modern stop motion looks amazing, but nowadays all most movie goers want to see is CGI and stuff blowing up ad nauseum. Modern movies are made for the cell phone generation, and they have next to no attention span.
It made a big profit at the box office. It cost about 9 million to make and made a 70 million profit.
There were rumblings of a sequel for around the next 10 years. Harry Hamlin talked about it in the early 90s. When he was asked about it, he jokingly said "Yeah, we can call it Perseus in a wheelchair."