Mark Hamill was doing a lot of stage work after Empire, during Jedi, and a few years after that. He felt more at home in Broadway than in Hollywood. He was Mozart in Amadeus on Broadway, and was also considered for the part in the film, but a studio executive turned him down because he didn't want Luke Skywalker to be in the movie.

In film, he was trying to get more parts that were different from Luke Skywalker. He probably got offered hundreds of shitty sci fi film roles in attempts to cash in on his name. He did voice work as early as the 70's, so his transition from stage to The Joker was an easy one. I'd say he's had the career he wanted.