The effects of POLTERGEIST can't be minimalized.  Starting with JAWS, continuing with CLOSE ENCOUNTERS and with the one-two punch of E.T. and POLTERGEIST, Spielberg created a genre that has since been mimicked in thousands of movies and TV shows -- the average suburban American family that finds itself dealing with an outside force it can't understand.   It might be aliens, spiders or shrunken kids.  It might be presented as broad comedy or comedy-drama but the formula rarely varied --- present middle class American characters who were excrutiatingly normal, contemporary and identifiable, living in messy TV- pop culture homes, dysfunctional but loving.  This was Spielberg's vision, carried on by proteges like Robert Zemeckis and Chris Columbus and practically every Amblin film ever made.   

I think the books of Stephen King contributed to this as well.  (I always thought the perfect King story would be titled "The Haunted Mac Donald's.")