I've really mixed feelings about Godfather III. It's not actually "a 5 star film" the way parts I and II are, but if you evaluate this film on its own merits, it's a deeply flawed film in terms of casting choices, but that doesn't take away from it. Yes, I and II stand on their own, but they also do anticipate that one day this story would need to be told.
Everything from the unconvincing incestuous relationship, dude in leather jacket becoming Capo di tutti capi, to glasses functioning as a murder weapon looks both awfully forced and naive for any crime film, and a tone too dramatic for a part of a very refined trilogy. It is obvious there was enough material and ideas solely to give it a basic temporal full circle.
As part of the greatest trilogy in cinema history it does suck. It's nowhere near as epic and emotionally packed as the previous parts. As a stand alone gangster film Its actually pretty solid and very well directed, apart from the cringeworthy performance of Sofia Coppola.
Michael Corleone's demise was as fascinating to see as Vito's. I was so glad when his daughter was shot in the end! My biggest problem with the trilogy were the scattered secondary/tertiary characters - even watching the films back-to-back in 4 days, I struggled to recall all their names and roles within the Godfather saga. But all in all, I see why these films are so highly-regarded by audiences and critics alike.
Third films are tricky and this one falls into that curse. Could it be that Part 2 was so great that it was impossible to top? Maybe. Or it could just be Coppola going through the motions again. This film definitely lacks passion but it is worth the watch just to finish the trilogy.