What are the chances you would leave a movie starring Denzel Washington and Russell Crowe shrugging your shoulders? That’s the dubious achievement of American Gangster. Based on actual players in the New York drug wars of the 1970s, Gangster stars Washington as Frank Lucas, who built a small Harlem crime outfit into an East Coast drug empire, and Crowe as Richie Roberts, a too-honest-for-his-own-good cop who ran the undercover unit that hoped to bring Lucas down. Director Ridley Scott is a visual stylist who needs cleaner material than the thick but skimpily detailed screenplay Steve Zaillian has provided, and neither Washington nor Crowe can make up for it.