As far as overall quality goes in a DVD picture wise and soundwise I would definitely asy the phantom menace DVD is a contendor. however, I wouldn't go as far as to say that its the best DVD I've seen quality wise by any means. Seeing the Matrix - special edition (which includes remastering from totally digital video sources rather than film) on a Sony Progressive Scan DVD player on a Mitsubishi HDTV and hearing it all through some Martin Logan Electrostatic speakers gave me a serious geek hardon. The picture quality on that DVD is so sharp its sickening. After Seeing the phantom menace on the same system I could see little weird artifacts in the colors during the pod race.
Braveheart is also another DVD that is mastered with excellent quality if you are looking for something to benchmark home theater and audio with.