Why do people think Stephen King is such a good writer?

Stephen King, much the same as Danielle Steele, is a niche writer who found his groove in black and white good vs. evil fiction. His early books, 'Carrie', 'The Stand', 'Salem's Lot', etc., appealed to the type of folks who loved 'Peyton Place' and 'Valley of the Dolls' for the quick if purple prose and simple, familiar and fantastical storytelling. He can spin a yarn, and people flock to that.