Basically, I agree with you: it didn't measure up to the others, but it was a fairly good movie. Problem is, enthusiasts like us can't really judge III as a stand-alone--nor should we because, for us, it isn't a stand-alone.

III had most of the elements that made the others great: big sweep, excellent performance by Pacino (and much-improved roles for Shire and Keaton), fine production, good music, action, etc. What it didn't have was a good plot--a huge flaw compared with the others. I've gone into the plot-gaps in other postings. For now, I'll just quote a friend who, after seeing it for the first time, observed: "Thare's probably 50 hours of film on the cutting room floor--and the plot is there, not here [the theater]."