First off, to me, Underrated director means someone who has consistently produced top quality films with very little recognition from their peers and does not routinely do well at the box office, but manages a huge following after the films have been released on home video. James Cameron does NOT fall under this category. He is not only an Academy Award winning director, but also the writer/director of not only two of the top 3 grossing films of all-time, but also the writer/director of 3 of the most celebrated Sci-Fi films of all-time (Aliens, Terminator 1 & 2). He has been consistently celebrated among his fans and his peers in Hollywood as one of the top directors of his era. Not underrated whatsoever.
For me, the most underrated director is John Carpenter - hands down. He's directed 2 of the top 5 horror films of all time (Halloween & The Thing). He has directed a who's who list of cult-classic films - Assault on Precinct 13, Escape From New York, The Fog, Christine, Star Man, Big Trouble in Little China, They Live, The Prince of Darkness, and Memoirs of an Invisible Man. Not only that, but he's also composed some of the most memorable film scores in movie history too.
Runner-up for me would be Joe Dante. He's the director of Piranha (1978), Rock 'N' Roll High School Forever, The Howling, Gremlins, The Explorers, Innerspace, The 'Burbs, Gremlins 2, Matinee, and Small Soldiers among others. His films are consistently considered among the most memorable and re-watched films of the 1980's and early 90's, yet the man's name is fairly anonymous and unknown despite this.
