More of a rough-edged, 70s-style cop flick than the gangster epic it was promoted as, Ridley Scott’s American Gangster is a consistently entertaining – occasionally stunning – movie built around two fine performances and a handful of scenes as electric as anything you’d see in an urban drama by Scorsese or Sidney Lumet.

The only problem is, it takes a little longer than it should to give up the goods.

Marred by a slow, shaky and narratively muddled first act – which certainly isn’t helped by the additional 18 minutes of footage included in the DVD’s “Extended Unrated Edition” – the film eventually establishes a compelling, energetic groove in its parallel stories of Harlem heroin kingpin Frank Lucas (Denzel Washington) and downtrodden cop Richie Roberts (Russell Crowe).

Washington is spot-on, as usual, as Lucas, who’s expectedly ruthless and calculating but also possesses a highly developed business sense, values loyalty and integrity, and sees himself as something of a man of the people. Inspired by his mentor, Harlem gangster “Bumpy” Johnson (Clarence Williams III), Frank goes to dangerous lengths to set up an unprecedented heroin-importing operation, buying uncut product from Southeast Asia’s opium-rich Golden Triangle during the Vietnam War and shrewdly using his military connections to ship it home. Determined to run his own business on his own terms, he begins seriously undercutting his rivals – selling better dope at better prices – and thereby secures his place at the top of New York’s criminal underworld.

Roberts, meanwhile, ends up shunned by his mostly-corrupt department when he refuses to keep nearly a million dollars in illicitly obtained cash; his personal life also in a shambles, he throws himself into a last-ditch gig heading up a ragtag (but honest) drug-enforcement squad tasked with locating the source of the ultra-pure “Blue Magic” heroin that’s begun flooding the streets.

Both of these stories provide enough juice to keep the film cranking along, but Scott and writer Steven Zaillian frustratingly take their time in getting things rolling and, worse, don’t really let us inside Frank’s head until after he’s returned from the Golden Triangle with his plans already in place. Once American Gangster finds its focus, however, it’s riveting almost through to the end, covering everything from Frank’s relationship with his devout mother (Oscar-nominated Ruby Dee) to Richie’s run-ins with a brutal unit of on-the-take cops (led by an especially surly Josh Brolin) while never losing sight of the escalating violence and disloyalty that put Frank and Richie on an unavoidable collision course with each other.

Their meeting comes fairly late, and those expecting Crowe and Washington to share a ton of screen time will likely be disappointed. But American Gangster does a better job than most films of bouncing back-and-forth between both sides of the law, as absorbing in its scenes of Frank’s rise to dominance of the Harlem drug trade as it is in those of Richie and his team’s ill-supported attempts to find out who’s running it. The sequences taking a Scorsese-like approach to the day-to-day operations of Frank’s business are particularly well-done and realistic; a late-in-the-game raid on a dingy New Jersey drug lab is as tense and well-directed an action scene as anything in Scott’s canon. Scott and Zaillian also conjure up some unexpectedly powerful scenes from Frank and Richie’s personal lives, revealing both as fleshed-out, flawed characters with well-defined codes of honor but imperfect consciences backing them up.

Crowe again impresses in a damaged, gritty, blue-collar kind of role, and the film features an excellent and appealing roster of supporting actors, including the great Chiwetel Ejiofor (Washington’s police partner from Spike Lee’s Inside Man), Cuba Gooding, Jr., Ted Levine, Common, John Hawkes, Armand Assante, RZA, and Joe Morton. They’re complimented by some very strong cinematography and production design that effectively recreates 70s Harlem from the glamour of the historic Muhammad Ali/Joe Frazier fight to the gut-wrenching squalor of drug-soaked slums.

For all it does right, though, American Gangster doesn’t quite have the scope or the visceral impact – not to mention the completely satisfying resolution – to put it on the level of its genre’s well-known classics. It’s a notch below Serpico and The French Connection, and at least two below Goodfellas, but those are big shoes to fill, and this is still a better American crime epic than anyone has made in a while. The film went through a number of stars and directors before ending up in Washington, Crowe, and Scott’s hands, but it ended up being a successful and enjoyable showcase for all three of them.

ON DVD: American Gangster makes its debut on disc in a couple of nicely rounded-out sets, both of which include the original theatrical version (running two hours and 38 minutes) and the “Extended Unrated Edition” (running two hours and 57 minutes) – myself, I’d stick with the shorter version, but it is pretty cool to have both. The two-disc special edition also includes two additional deleted scenes, a five-part behind-the-scenes documentary, and a three-part “Case Files” documentary discussing the film’s nods to realism in its drug-bust sequences; the three-disc Collector’s Edition also throws in two music videos, a featurette focusing on the several hip hop artists that have roles in the film, two music videos, TV segments from BET and NBC on the making of the film, and a digital copy of the Extended Unrated Edition.