Well ROTJ is in my opinion completely on a par with SW and ESB. Yes it does have some "silly" things (like Ewoks) but SW and ESB have their share of "silly" things too. After all these are fantasy films.

Maybe ESB has a little better acting but that is reasonably so because the story/script offered a bit more and because twice as much time was spent on principal photography compared to either ROTJ or SW.

As for prequels, the main problem I have with them is that it is not an adventure/fantasy any more. It is a soap opera about an annoying repulsive main character. And I don't enjoy that...