What movie changed or created the cinema as we now know it?
Black Christmas basically created what is known as the slasher genre. John Carpenter's Halloween took cues from the direction of Black Christmas (which is now known as the point of view shot)and just added to it. Halloween could also have been inspired by Psycho somewhat and possibly Peeping Tom too. Even Friday The 13th got inspiration from Halloween for example, when characters get killed off because of something they did wrong such as drugs or sex, but the wholesome girl survives. Because of Black Christmas, Halloween was made which created a domino effect that led to other slashers such as Slumber Party Massacre & Terror Train.
Flashdance helped put leg warmers on the national map.
http://www.youtube.com/watch?v=6Vx4J_NtNPk