There’s a reason the “Friends” demand such a high price tag for their series: their feature films tend to suck.

With the exception of Courtney Cox-Arquette in the “Scream” trilogy, a “Friend”-ly film can’t make bank to save its life. Matt LeBlanc’s “Ed,” David Schwimmer’s “Pall Bearer”–if you’re scratching your head trying to recall these cinematic masterpieces, that says it right there.

Consequently, the sextuplets turn in half-assed performance after half-assed performance, with their television paychecks softening the fall. Most recently, Matthew Perry can be seen slumming it with Liz Hurley in “Serving Sara,” a painful experience that has viewers longing for “Almost Heroes.”

So it’s both a blessing and a curse to have Jennifer Aniston star in the Sundance darling “The Good Girl.” Aniston, along with the supporting cast, is fantastic but can only do so much to overcome the otherwise empty film.

As the small-town Justine, who feels imprisoned in her discount-store-shaped cell of a life, Aniston’s emotional performance rescues the film from its own monotony. She looks her most unglamorous yet in this role, but she’s still adorable as she shuffles her way through her unfulfilling marriage to well-meaning, but perpetually stoned Phil (John C. Reilly, “Magnolia”) and her dead-end job at the Wal-Mart-esque Retail Rodeo.

Justine finds love, or at least an escape, in her young co-clerk, Holden (Jake Gyllenhaal–who, incidentally, is making a habit out of affair-ing with attractive older women–he bedded Catherine Keener earlier this summer in “Lovely & Amazing”) and the two begin a secret affair, again in the very unglamorous way of making out in the stock room and shagging at a seedy motel.

Gyllenhaal (“Donnie Darko”), as usual, plays the troubled aspiring writer with an added complexity that many Freddie Prinzes-come-lately could never attain.

Gyllenhaal, Aniston, and the rest of the cast all turn in excellent performances, and writer Mike White (“Chuck & Buck”) again shows his intricate, screenwriting potential. But when it comes down to it, “The Good Girl” is a film full of potential that never quite delivers.

The acting can never get beyond all the doubting White’s script creates. Is the affair between Holden and Justine based on love or just lust and boredom? Is Holden the talented, troubled writer (his samples suggest otherwise) or a crazy, drunk kid? And perhaps most importantly, is Justine a victim of her own existence or a victim of her own stupidity?

When Phil’s best buddy Bubba (Tim Blake Nelson, “Minority Report”) discovers Justine’s infidelity and blackmails her into sleeping with him, we begin to question her common sense even more. When she discovers she’s pregnant, we are almost fed up with her all together.

And perhaps that’s what White wants us to do. Much like last year’s indie gem “In The Bedroom,” “The Good Girl” is a peek inside the lives of real, unglamorous people with unglamorous problems and unglamorous (very unglamorous if you remember Nelson correctly) ways of dealing with them.

And like many indie “gems,” (“Bedroom” excluded,) “The Good Girl” lacks a focus, creating too much reality and too little purpose. There are moments when you identify easily with Justine, and then there are moments when you shake your head, frustrated at another bad decision. If it weren’t for Aniston’s inherent likeability and her talent, “The Good Girl” would have been one bad movie.

GRADE: B/C