I find them all great movies in their own genre. I almost never say any particular film is the best of its kind, merely amongst my favorites. Keeps me from having to rate them specifically.

Other Genres but in no particular order;

Anime: Akira, Princess Mononoke, Howl's moving castle, Ghost in the Machine, Crying Freeman, Neo Evangelion

Horror: Hellraiser 1 & 2, The Exorcist, Night of the Creeps, Dead Alive (aka braindead), Return of the Living Dead, Halloween (original)

Korean: Oldboy, A Bittersweet Life, The Good The Bad and The Weird, A Tale of Two Sisters

Surrealist: Anything David Lynch, Most Lars Von Trier, Rubber, Most David Croenenberg

Porn: Your Mom (Sorry, couldn't help myself)