The difference between ROTJ, the admittedly last-place of the OT, and the entirety of the PT is that ROTJ makes sense, has some sense of narrative and functions as a film, rather than (simply) a merchandising vehicle.
Move your sights to Empire and all bets are off. Empire is a fantastic film, full stop. It's full of witty dialogue, character intrigue, relatable romance and genuine performances. You can't say that about any of the PT.
They're just bad movies: they take talented actors and strip them of all their talent. We get Ewan McGregor and Samuel L. Jackson reduced to flat line-readings. The action is nonsensical and the persistent green-screen sets rob the films of the immediacy and tactileness that made the world of Star Wars so engaging. The scripts are beyond dumb and the direction is dull and lifeless.
But the kids love em. And that's great. Kids loved the OT too. Difference is, so did their parents.