Having not seen the Godfather films (the first two, IIRC, were adapted by the original novelist, Mario Puzo) nor Gone With the Wind in there entirety, I can't really say, but perhaps this is because the changes were wholly successful?
Further question about ending:Do they go by the tower of Minas Mogul? Do they reach the part where Sam and Frodo hide under the bridge as the soldiers of Mordor pour forth above them? I am dissapointed that Shelob (and therefore Frodo's apparent death/capture) has been pushed to movie 3...