Generally, the fans of the old three Star Wars movies hate the prequels because they rely on CGI way too much, whereas the original trilogy used puppets more than anything else. They believe that the original movies achieved much more depicting this whole world without any fancy technology that the newer movies had. Also, the acting and cast in the original trilogy is better than in the prequels, with fans mostly hating Hayden Christensen for his portrayal of the young Darth Vader.