How the toys of our youth lose their charm when thrust huge and noisy onto the screen. First, it was the Transformers, reduced to inelegant CGI monsters by Michael Bay’s effects crew. Next up? The real American heroes of G.I. Joe, whose back-stories are at least acknowledged by director Stephen Sommers (The Mummy, Van Helsing), but whose charisma is all but eclipsed by the movie’s raison d’être – namely, deafening explosions and expensive-looking set pieces.