Hollywood's summer box-office streak has cooled a bit with a $37 million opening weekend for J.J. Abrams and Steven Spielberg's sci-fi tale "Super 8." It was a healthy but unremarkable launch in a summer season whose newcomers often open with two or three times as much money. Released by Paramount Pictures, "Super 8" largely features a cast of young newcomers, the story centering on teen filmmakers and an alien entity that escapes from a wrecked train. "The movie was never conceived to...