What?!?!? A contrarian in our midst? Are you perchance a democrat? :-) :-) :-)
All kidding aside, although III doesn't reach the lofty standards of its predecessors (II is my favorite of the trio), I personally like it a lot.
It's become de rigueur to throw GFIII under the proverbial bus. I think it finishes out the trilogy well and, if nothing else, it ensures no more Roman Numerals for the Godfather sequence (unlike the Rocky series).
Plus it gave us the memorable quote from Michael Corleone: "Just when I thought I was out... they pull me back in."
GF 1 & 2 were made just 4 years apart. The characters for 2 were well known and liked by the movie goers. It was easy for the audience to pickup the story with #2, which in turn enhanced the appeal of 1.
GF 3 was made 20+ after 1 & 2. Almost an entirely new cast.
Coming so far after the first two movies, it was difficult for the movie going audience to connect with the characters as they had in 1 & 2. Having said that, the third installment was not up to the level of 1 & 2. The Godfather growing old was not as compelling a story as the choir boy being converted to a hardened gangland boss. Don’t get me started on Sofia Coppola in #3. That was just a mistake.