The success of “Obsession” and “Backrooms” may mean some studio bosses will place a few more bets on original concepts rather than predictable franchises and sequels.​ The biggest two movies in America right now, “Backrooms” and “Obsession,” come from twentysomething filmmakers who honed their craft on YouTube. Their films were made with relatively low budgets and were marketed online. Now that they’re filling theaters with teens and young adults who rarely show up at the movies, all of Hollywood is paying attention, with experts predicting that studios will copy this moviemaking model many times over. “Obsession,” directed by 26-year-old Curry Barker, opened