I'm not sure. It seems people here vote only for american movies, though.
I'll say the 80's, but I am highly influenced by a nostalgic feeling, even if most of those movies I hadn't seen back then.
Ghibli was formed. It was the beginning of Miyazaki's career as a movie director (he had previously directed tv series, and the legendary Castle of cagliostro, but his full artistic power came primaly with Nausicaa). We got Nausicaa, Castle in the sky and the wonderful Totoro. With Takahata we got the musical Goshu the cellist and his masterpiece Grave of the fireflies.
Mamoru Oshii (ghost in the shell) really discovered himself in the 80's. With Beautiful dreamer he got to show the world what he could do. Angel's egg is still the greatest adaptation of Amano's artworks. And Oshii's most crazy movie. Patlabor (89) got released, and was (and still is) a masterpiece. The first movie by Oshii stand alongside his two ghost in the shells and Angel's egg.
AKIRA was release. I won't sat anything else about that, the word itself speaks volume enough.
Jim Henson got to his peak with his two masterpieces: The dark Crystal and Labyrinth. Two of the greatest fantasy movies ever put on films. Henson and Oz were gods.
(and two other muppet movies were released by Henson also in the 80's.)
While I consider the 70's to be Spielberg's most important decade, his last two indiana jones movies, his E.T., and his Empire of the sun were all spectacular movies. E.T. is one of the only live action children movie to ever having been able to compete with Jim Henson's movies (of course, Miyazaki's Totoro is still miles ahead of all of those, though).
While Jackie Chan was discovered in the 70's, (and so were Samo Hung and Yuen Biao) it was in the 80's their carreer exploded (and the quality also). Jackie Chan released his phenomenal Police Story trilogy (though I think the third one was release in the early 90's) and truly changed the face of police action movies in the world. And even better, the three brothers (Chan, Hung and Biao) began making movies together. Project A, Wheals on meals and Dragon forever are still 3 of the greatest and most fun kung fu movies ever put to film. Seeing these three incredible actors and martial art fighters together on the screen is joy from beginning to the end.
John Woo was discovered. We would never had the matrix and all of these heavily action oriented gun movies if it wasn't for the release of the first A better tomorrow (followed by both the second A better tomorrow and The killer, all monumental movies in their own field). Woo is a legend, and these are the movies why.
The thing and Shining were release. What I consider the two best horror movies out there, so for me of course this is pretty important.
There are many other factors, of course, but these are my most important right now this morning (the coming of tim burton with his beetlejuice, batman and Edward is probably a factor many would name, for exemple).
But yeah, the 80's rocked!