The Shawshank Redemption is a film that people who like mainstream Hollywood films think is the best film of all time. People who like cinema more broadly tend to rate it much less highly. The former think the latter are pretentious gits, the latter think the former don't get the 'art' of film.
I don't think The Godfather Part 3 is as bad as some people say, but then again I don't think the first two are quite as good as people say. I will not hear a word against either The Deer Hunter or Apocalypse Now, though.