Alfonso Cuarón is one of my favorite directors. He made the best Harry Potter films, The Prisoner of Azkaban; the fantastic and memorable Children of Men, which is, at least on one level, a retelling of the Christmas story, and the thrilling, head-spinning Gravity. These movies are so different from each other, it's basically impossible to pin down a signature style or trademark. Cuarón just makes great films, plain and simple.

Roma, a domestic drama about a middle-class Mexican family in the 1970s, is a return to Cuarón's roots. The heart of Roma (named after a barrio in Mexico City) i...