I have only seen the first three films, haven't read the books, and even I know that Voldy wanted Harry dead to prevent Harry from killing Voldy. The parents were only protecting Harry. I have no idea if I learned this from three movies or from cultural osmosis.
PS - My plan is to rewatch the first three films and continue onward. Ever since I tested positive as Slytherin in the HP test, I also knew that the filmmakers were trying to sully the Slytherin name. That's a lot of nerve thinking all Slytherin are villains. The kind of nerve that makes me want to see Griffyndorks fall into an empty hotel pool, the kind of falling that happens because I had pushed them!