Never mind The Avengers. The real superhero in theaters right now is Supreme Court Justice, Ruth Bader Ginsburg, the focus of “RBG.” 

More valentine than documentary, the film is a spritely and affectionate tribute to the 84-year-old judge and unlikely pop-culture phenom who, like some fairy godmother many of us never knew we had, helped change the landscape of women’s rights in 20th and 21st century America.