I don't think this counts. It was the highest grossing movie for its year of release and a huge movie worldwide at the time. It certainly wasn't underappreciated back then and ignited the entire disaster genre. Had a great poster too.
Almost all 'old' movies are underappreciated in time, so are we talking about films that were good but went unnoticed by the audience when they were released or any film thru time that is just currently under appreciated by today's audiences?
