SELENA — ★ ★ — Jennifer Lopez, Edward James Olmos, Jon Seda; written and directed by Gregory Nava.; rated PG (violence, mild profanity)

"Selena" had the potential to be a terrific, real-life rags-to-riches Hollywood bio. And when film-

maker Gregory Nava concentrates on the struggles of Mexican-Americans in the United States, or on this particular family's efforts to remain close in the topsy-turvy world of show business, "Selena" is, albeit briefly, compelling stuff.

But writer-director Nava could have used some help on the script, which settles for backstage show-biz cliches and unimaginative music videos, forcing "Selena" squarely into the run-of-the-mill category. (And at 2 hours, 10 minutes, it's way too long.)

On the other hand, there's Jennifer Lopez's starmaking performance at the film's core, and Edward James Olmos lends some heft (in more ways than one) as her father. And 10-year-old Becky Lee Meza is quite good as the younger Selena.

But the result is, sadly, a hit-and-miss affair.

For those unfamiliar with the "Tejano" singer from Corpus Christi, Selena Quintanilla Perez was a Mexican-American pop music star who had won a Grammy, managed to land five albums on Billboard charts at the same time and was just about to cross over to an even larger Anglo audience when she was shot and killed by a mentally unstable older woman, the president of her fan club.

The movie unabashedly paints her as a saint (not too far removed from the status a lot of teens have given her since her death), a young woman whose strong family ties kept her on the straight-and-narrow.

In fact, the worst thing she ever did was get married at age 20 against her father's wishes . . . though, as the film portrays it, she and her rock guitarist husband made peace with Dad the next day.

Olmos is very good in his complex portrayal of a man who sees an opportunity to revive his own failed musical aspirations through his talented daughter. Overweight and undertalented, Abraham Quintanilla guides his daughter's career carefully and tries hard to keep his family together. He also strives to keep a sense of balance between their Mexican heritage and their status as American citizens.

In fact, there are a couple of nice monologues spoken by Olmos on this subject, including a riveting moment when he explains to Selena that she must embrace her roots if she's ever going to succeed in life — which helps her to find her own voice in the musical world. (The real-life Abraham Quintanilla is the film's executive producer, and he allows Olmos to develop a conflicted characterzation, warts and all.)

When Dad forms a small band with Selena and her siblings, Mom (Constance Marie) thinks he's gone around the bend. But after a time, and a lot of hard work, the group takes off — and Selena becomes a star.

Lopez is having quite a year — she also co-stars with Jack Nicholson in "Blood & Wine" and with Ice Cube in the thriller "Anaconda," both upcoming — and she really shines in the title role, demonstrating Selena's ability to combine innocence and sexuality on the stage with a down-to-earth quality that audiences found quite charming.

But a number of other characters get short shrift (we never learn much about her siblings, for example), and the film's climax, culminating in her death, feels rushed.

"Selena" is rated PG for the violent climax and a couple of mild profanities.