A New Hope is solid. You can find blemishes, and they've torn new ones with the "special editions" that just cram more CGI shit on the screen for no reason, but as a classic Hero's Journey movie A New Hope works rather well. It was amazing for its time; I mean, a fun Sci-Fi movie? With special effects this good? It was a cultural phenomenon for a reason.
The Empire Strikes Back is the best Star Wars movie that has been made, which is why when most people quote Star Wars they're actually quoting Empire. The characters are at their deepest, the setting feels the most magical, and the Luke/Vader saber fight is utterly gripping.
Return of the Jedi was the beginning of the "Lucas is a genius who can do no wrong, do everything he says" era. The "let's put a funny thing in the background" starts happening. We get Jabba's hedonism palace with the droid torture room, Bikini Leia, Ewoks, and lightning hands Palpatine. This would only get worse by the time the prequel trilogy is made, Lucas gets to make whatever he wants without question.