I'd say that he isn't an easy listening joke but he has plenty of pop appeal.
The material from the beginning of his career is pretty forgettable. He was pop folk, had some hits and got a lot of representation from his label as a guy who was going to go somewhere.
He then got tuberculosis and almost died. The next two albums after he recovered were the ones that he is remembered for. Almost all the songs you posted are from those albums. Trouble is about battling TB. He lost a most the pop star patina and got to join the heavy singer song writer cannon.
Don't know how many albums he made between TB and becoming a Muslim but after he became a Muslim he didn't release anything for a long time. Started putting out albums after the break which are pretty forgettable.
Have you seen Harold and Maude? The soundtrack is all his stuff, it's a great film which his music complements nicely.