i think the answer for "why some great non-english masterpieces are underrrated" is because unlike Hollywood productions, foreignfilms are hard to understand ( for sometimes i see some movies of unfamiliar cultures to me)and to evaulate,to criticise,to find( yes there are dvds of most of them but what about the rest?),mention about( cos i could find no body till i have found this site to talk about non-english movies)...
in order to get the full taste of foreignfilms you should have a profound culturel-historical-social background of that nation!
for example: Yol-1982 ( The Way) when i read critiques of some people who have seen it, i imeediately realize that almost nobody could understand it except a few who had a bit knowledge of that time of Turkey...
i think that is why ( beside the handicaps to find them ) some masterpieces films are underrated...!!!