A remake of the beloved 1984 underdog classic, “The Karate Kid” is not quite the movie it should be.

Overlong, sputtering and aimless at times — and cheesy pretty much throughout — the film still manages to pack in an astounding number of stand-and-cheer moments toward the end. Thus, in what has largely been a forgettable year for the blockbuster, “The Karate Kid” may well be the best that summer 2010 has to offer — even if it falls well short of the original.

The film stars Jaden Smith (most memorably seen alongside his famous father Will in “The Pursuit of Happiness”) as Dre, a Detroit youngster who has to move to China with his mother. Apart from its changed setting and character names, the story closely resembles that of the original: Dre meets a girl in Beijing, but some mean bullies keep messing with him every time he tries to talk to her.

After one particularly painful beat down, Mr. Han (Jackie Chan), a maintenance man and secret kung fu master rescues young Dre, who asks Han to teach him kung fu. Han agrees after seeing firsthand the ruthless philosophy Mr. Han is passing along to his students — the same kids tormenting Dre. After many painful training sessions, with the usual underdog-story angst and adversity, Dre competes in a kung fu tournament, facing and defeating the bad guys.

For all the film’s shameless clichés, it’s made watchable, and occasionally enjoyable, by superb performances from its two stars. Smith’s performance is fresh, energetic and surprisingly believable. That he has the same mannerisms and something reminiscent of the swagger that made his father one of the world’s biggest movie stars certainly can’t hurt. Young Jaden even drops a hip-hop track on the film’s soundtrack, as Will Smith did in so many of his biggest hits. (Regrettably, the track also features Justin Bieber, but still.)

And Chan, as he has done in nearly every recent role of his, brings a good deal of grace and solemnity, along with unmatched kung fu skills. Although his role is hampered by a needlessly meandering character back-story, Han is a worthy replacement for the venerable Mr. Miyagi — humble and understanding, but also funny and blunt when needed.

With a grueling runtime of nearly 140 minutes — well beyond the attention span of the film’s key demographic — “The Karate Kid” nearly exhausts the considerable charm of its stars and the patience of its audience before Dre’s kung fu training even begins. But when the uplifting, musically enhanced scenes of sap and sentiment finally appear, viewers will be all too willing to cheer out loud.

It’s clear, then, that “The Karate Kid” is a film to love, even if it isn’t all that good.