Sandwiched between the first two Godfather films, Al Pacino made his first (of two) masterpiece(s) with director Sidney Lumet , Serpico (1973). The second arrived two years later in Dog Day Afternoon . It's a shame the two never worked together again after that. While the systemic corruption exposed in Serpico (based on the real life of police detective Frank Serpico ) probably felt more eye-opening in 1973, the film itself has aged incredibly well, thanks in large part to Pacino's all-in (and mostly restrained) performance, the quasi-documentary quality, the interesting editing, and the time capsule of the period (you can't deny Pacino's outfits and facial hair phases). Sidney Lumet Feature Films Ranked Top 20 Directors