"Books"
Science Fiction: Jurassic Park - Crichton (1989)
Runner Up: I Robot - Asimov (1950)
Fantasy: The Hobbit - Tolkien (1937)
Runner up: .... I guess I seriously dont read enough fantasy. All I can remember was the other Tolkiens (which were solid) and Martins series (and those felt like polished (and more gruesome) Tolkien)
Dystopian Fantasy: Nineteen Eighty Four - Orwell (1949)
Runner Up: Battle Royale - Takami (1999)
General Fiction: Watership Down - Adams (1972)
Runner Up: Sirens of Titan - Vonnegut (1959)
Probably could make the arguments for more classical works that the above are built upon... but these were the peaks of the genres, so being in the last century makes sense.
"FIlm"
Science Fiction: 2001: A space odyssey (1968)
Runner Up: Planet of the Apes (1968)
Fantasy: The Dark Crystal (1982)
Runner up: Willow (1988)
Dystopian Fantasy: The Road Warrior (1981)
Runner Up: Children of Men (2006)
General Fiction: The Fountain (2006)
Runner Up: Twelve Monkeys (1995)
Edit: Should Probably add "Games" since this is GAF.
"Games"
Science Fiction: Mass Effect 2
Runner Up: BioShock
Fantasy: Final Fantasy 6
Runner Up: WarCraft II
Dystopian: Death Stranding
Runner Up: Fall Out: New Vegas
General Fiction: Monkey Island (series)
Runner Up: Red Dead Redemption 2
Further Edit cuz
FunkMiller
brought up comics a few posts down.
"Comics"
Super Hero: The Age of Apocalypse (multiple comic series spanning story arc) - Marvel
Runner Up: The Watchmen - DC
Science Fiction: Star Wars: Crimson Empire - Dark Horse
Runner Up: Star Wars: Star Wars: Shadows of the Empire - Dark Horse
Manga: Akira - Kodonsha Comics
Runner Up: 20th Century Boys - VIZ
Other: The Walking Dead (1-96... aka until Hill Top, but pre Nagan ) - Image
Runner Up: Y: The Last Man - Vertigo/DC