In a world ... where one man ... voices THOUSANDS of the world's most recognizable movie trailers -- it's really really sad when that guy passes away.

Hal Douglas -- the gravelly voice behind trailers for movies like "Philadelphia," "Forrest Gump," "Meet the Parents," "Lethal Weapon," and way way more -- died Friday due to complications from pancreatic cancer ... his daughter said.

Douglas passed away at his home in Lovettsville, Va. He was 89.