Part III doesn't bother me as much as it does other people.
Granted it is far from a great movie, but I still find it a good movie if you overlook some of the flaws.
Part III is flawed when compared to the first two films, but that's the danger with any sequel. The first two films set the bar so high that it was nearly impossible to attain such levels in the third installment. Taken on its own, III is a pretty good movie. It has some excellent moments, but also has some weaknesses, which have been outlined on these boards many times. The main difference is that the first two parts had no real weaknesses.