“John Wick” opens Friday at Point, Eastgate and Star Cinema. R, 1:48, three stars out of four.

Why does “John Wick” work so well and “The Equalizer” didn’t? Both are action revenge films where a lone warrior sets out to correct a relatively minor injustice by wiping out an entire Eastern European-based mob. Both even have the requisite “walking away from an explosion” shot.

But while I found “The Equalizer” to be plodding and joyless, Chad Stahelski’s “John Wick” is a pure blast of R-rated fun for action movie fans. It has some of the most inventive, beautifully-staged action scenes I’ve seen a while, a sense of style, and even some moments of black humor.

And — dare I say it? — Keanu Reeves just out-acts Denzel Washington. Reeves plays Wick, who is a cipher when we first meet him, a quiet man grieving the loss of his wife (Bridget Moynihan) in their New Jersey home. A few days after the funeral, a puppy shows up on his doorstep, bought for him by his late wife. Reluctantly, he bonds with it.

But then, at a gas station, Wick’s ’69 Mustang is coveted by hotshot young Iosef (Alfie Allen). Wick blows him off, but Iosef, who turns out to be the son of mob kingpin Tarasov (Michael Nyqvist). So he brings some goons to Wick’s house to steal the car, beat him up, and kill the dog.

When Tarasov is told of his son’s actions, he responds with a simple “Oh.” Because he knows Wick used to be the underworld’s most lethal assassin, in the I-once-saw-him-kill-three-guys-with-a-pencil mold. The retired Wick breaks out the artillery, and it’s game on, as Wick slaughters his way through nightclubs, hotel rooms and churches on his mission to kill Iosef.

Stahelski is a former stuntman (he was Reeves’ stunt double in “The Matrix”) who clearly has a reverence for the brutal ballet of fight scenes. Rather than rapid-fire cutting, he lets a shot hold for a few seconds, as we see Wick shoot three or four guys with merciless precision, or trade blows in close quarters combat. There’s one shot where we see Wick and a goon struggle over a knife that must last 30 seconds or so, which in modern action movie terms is the equivalent of the opening tracking shot in “Touch of Evil.”

It’s thrilling and kinetic, and Reeves’ feline grace onscreen, even at 50, makes him a perfect avatar to follow — the fact that he’s grieving and a little rusty at his skills makes him an appealingly vulnerable sort of killing machine. The world that Stahelski and screenwriter Derek Kolstad build around him is lots of fun too, full of bright reds and greens and purples, and peopled with rich supporting cameos by Willem Dafoe as a rival assassin, Ian McShane as a philosophical underworld type, and Lance Reddick (“The Wire”) in a very funny part as an unflappable hotel concierge who never gets flapped by the mayhem in his establishment. Nyqvist also turns in a sly, knowing performance that rises above the usual Big Bad part.

By the end, “John Wick” breathes life into a genre that one might have thought was exhausted, and I wouldn’t mind seeing it launch a franchise as long as all the same players are in place. I just hope that, next time, Wick doesn’t buy a cat.