“I always tell the truth, even when I lie,” Tony Montana said in “Scarface.”

We all know the formula: First you get the money, then you get the power, and then you get the respect.

Ridley Scott’s new film, “American Gangster,” assumes that you bring that knowledge with you into the theater, and it faithfully adheres to all the requisite conventions of the genre with avid energy and the unrelenting directness that the title suggests. The film’s greatest achievement stems from its energetic revival of and homage to gritty New York crime films of the ’70s: Imagine a movie that is equal parts “Serpico,” “The French Connection” and “Superfly,” all held together by a classical, rise-to-the-top mob narrative.

Unfortunately, that blending causes the film to suffer a mild identity crisis. It moves in a lot of directions and never finds time to examine the moral conflicts, or lack thereof, beneath the calculating yet charismatic exterior of legendary Harlem crime lord Frank Lucas. Emotions run high but remain superficial, which keeps this good film from joining the crime epic pantheon among the likes of “Goodfellas,” “The Godfather” and “Scarface.”

But let’s look at the positives for a moment. First of all, the facts of Frank Lucas’s ascendancy in New York crime, as well as the methods he used to achieve his status, are nothing short of amazing, unprecedented and damn entertaining. After the death of his boss and mentor, Bumpy Johnson, Lucas (played by Denzel Washington) devises an ingenious plan to fill the power vacuum in Harlem.

By using some enlightened business techniques, namely cutting out the middleman, he plans to maximize the profits from his principle product: heroin. With the help of a Marine Corps cousin stationed in Vietnam, he manages to buy pure heroin straight from Southeast Asia and put it on the street at half the price, eliminating almost all competition. His “Blue Magic” brand of heroin puts him at the top of the game. Scott and writer Steven Zaillian pace the film beautifully, moving deftly from rice paddies in Vietnam to a Bobby Womack-infused montage showing Lucas installing his North Carolina brothers in various drug fronts.

At the same time, an honest Jersey cop named Richie Roberts (played by Russell Crowe) makes waves in the department by, well, being honest in an institution overrun with corruption. He becomes an outcast in the eyes of fellow cops when he turns in a million dollars in cash swiped by a crooked cop from a drug deal. Bolstered by a passing grade on the New Jersey bar exam, Roberts forms a renegade task force in order to make a name for himself and track down the source of the new, ultra-potent heroin hitting the streets.

Even though Lucas and Roberts don’t appear in the same room together until the last 10 minutes of the movie, the powerful similarity between the characters compels us to root for both sides in a classic “cops and robbers” way. Washington and Crowe both pull off expert, blockbuster turns as two strong, morally opposed men that exude an effortless charm and are also not afraid to piss people off to get what they want. The excitement, humor and tension present in their face-to-face meeting might cause the audience to wonder why they didn’t meet sooner.

The underlying answer to that question brings up the film’s biggest flaw: an absence of any sort of emotion in Washington’s character. Scott intersperses many scenes depicting Lucas’ opulence with junkies shooting up and dying, supposedly to show Lucas’ disregard for the fact that his riches are made from the misery of others. But even when his own mother slaps him in the face for his actions, we see no emotional resonance or humanity that might suggest his regret. He remains a two-dimensional archetype instead of a fully formed character.

Every iconic gangster of American film since the 1920s has thrived on the same contradiction: that he can hold the people around him to a certain code of ethics, above the modern conceptions of morality and law, without being subject to that code himself. Audiences identify with these characters, because they feel free to accept that code and their own position outside it with the same righteous impunity. They enact all their dirtiest desires vicariously through the brutal murders and crimes of the protagonist, who usually misappropriates his actions and ideals with misnomers like “business” and “respect.”

The great gangster films depict criminals coming up against the effects of their own hypocrisy, like Montana’s persistent unhappiness or Corleone’s self-destruction of the family he was supposed to protect. Lucas remains too composed, even in the end, to let the audience register who he really was.