Again, it's all a matter of opinion.
Most of nohandluke's points have merit and (I think) would reside in the majority of Star Wars fans' hearts, but it's his opinion. -1 believes differently and makes his points. Both posts seem a little on the argumentative side for those on the opposite side of the fence, however. I personally don't feel Revenge of the Sith is anywhere close to the quality of The Empire Strikes Back, but to each his own.
I agree with nohandluke for the most part. In my opinion, ESB (1980) ranks as one of the few movies I consider to be 'perfect' as well. Yes you can argue technical, creative, and narrative points about the film, but let me explain my position.
Watching the movie for the first time (or one hundredth for some:) ), one can get the emotional and visceral impact of the film. The pacing is spot on, the direction is great, the cinematography superb, and the music is perfection personified (John Williams best score by far, and a masterpiece of composition from start to finish). It built on what Star Wars began and brought it to levels unseen. Star Wars is a great film, but suffers from more technical difficulties than ESB as well as some pacing issues (I've watched with some first timers and they've gotten bored with Tatooine in the beginning; for good or bad they just wanted to get on with the story). I don't think of the original Star Wars as a perfect film, though. ESB can slow a little post-Hoth, but the Jedi training is juxtaposed nicely with the Falcon's escape and keeps things interesting and the film moving.
Does ESB function as a stand alone film without SW and ROTJ on either end? Probably not**. But those seeing it have already seen Star Wars and the cliff hanger ending makes one want to see Return of the Jedi. It takes the "heroes always triumph" modality Star Wars maintained and flips it on its head, showing that the bad guys do win sometimes. This robs the viewer of his or her "always safe" feelings for the protagonist and provides tension for the rest of the show and series.
I think this is why ESB has struck such an emotional chord with people around the world. It's not a safe movie. It moves quickly. A lot of new ideas are presented. Old notions are explored. No one is safe.
Again, different tastes for different people, but The Empire Strikes Back simply FEELS like Star Wars to me, and I get the same feeling every time I watch it (a feeling any of the three prequels failed to catch, in my opinion). It is perfect in my eyes from an overall product standpoint, but with Ady's help, all the little technical nuances that stand out to some will be tweaked and a potentially superior product will come of it. The original 1980 film will always be the gold standard, but a visually tweaked version performed by a skilled artist with respect for the source will be a welcome addition indeed.
**This would make for an interesting experiment. Try to find someone who knows nothing about Star Wars. No Vader, no Luke, no Force, nothing. Show them The Empire Strikes Back without seeing Star Wars first and then gauge their reaction. Did they like it? What impact did it have? I'd like to see this done some day...