A New Hope has the most problems, and not where you think. The glaring example is when Grand Moff Tarkin grills Princess Leia for the location of the rebel base or he would toast Alderan. This is simply a conversation between the two, but as the scene cuts from one shot to another, the audio quality rises and drops notably. One angle sounds soft and muffled, while another angle is clear and sharp.
...It also mention very notable scan lines in Ep. IV. and gave the video and 8/10. The guy that was remastering the picture said he could have used another year.
Nice.