I think Return of the Jedi was a more disappointing movie. The change in tone in this from Empire was more drastic than the change between this and the prequels.
I don't know, I rather like the part at Jabba's palace. The rest I don't think was as good as Empire but still good stuff. Speeder bikes, cooler Death Star battle, Jedi showdown... Maybe a bit unimaginative (another Death Star... Really?) but good times.
Evolution is a million line computer program falling into place by accident.