Revolutionary it is not — it will do about as much for “gay cinema” as last year’s “Alexander.” Nevertheless, Ang Lee’s unforgettable “Brokeback Mountain” is a cinematic masterpiece, now atop an Olympian throne of critical acclaim, that, when watched, chooses a more near-earth existence. It steps down from its skyward pedestal and wrestles with themes near and dear to every human being — love, nature, regret — with unprecedented objectivity and sheer beauty.

The story follows the entanglement of ranch hands Ennis Del Mar (Heath Ledger) and Jack Twist (Jake Gyllenhaal) who herd sheep one summer atop Brokeback Mountain but end up, as their boss Aguirre (Randy Quaid) puts it, “stemming the rose.” Brokeback Mountain becomes for Jack and Ennis a lovers’ paradise paradoxically flawed and perfected by its transience and permanence.

After the gig abruptly expires, the men say goodbye and try to move on with their lives, leaving Brokeback Mountain, and each other, to haunt their dreams. Ennis marries, begets children and is unaware that Jack has done the same until a postcard suddenly arrives in the mail, four years after Brokeback, requesting a reunion. Ennis assents and before long they are right back at it again, first in a neon-lit tryst in a motel room and later returning to the wilderness for extended solitude, living their double lives and growing old as little more than “fishing buddies.” Their relationship, though, exists more as an elusive idea than a reality. The two men face conflicts about their future but never get tired of each other, never concede the possibility of recovering a piece of Brokeback — the experience, and image, to which all others pale in comparison.

Ang Lee, a director mature enough not to rely on mere acting to make a good film, nevertheless stumbled upon a gold mine when he cast Ledger and Gyllenhaal. Both give subtle, nuanced performances that are, for each, the best of their careers. Gyllenhaal’s Twist is windy and romantic, a droopy-eyed flirt to boot, but beneath the rim of that cowboy hat lurks something darkly sensitive, magnetic and even dubious. And Ledger’s stoic, staggering Ennis silently screams psychological complexity without revealing more than a few harnessed details about his life.

It may come as a surprise that there are females in the film, enough even for a “Women of Brokeback” Playboy cover. Michelle Williams is first among them as the miserable Alma Del Mar, a character who elicits sympathy while conveying a sense of the moral ambiguity inherent to her situation, while Anne Hathaway’s assertive Mrs. Twist illuminates the screen. And it is difficult to ignore a resplendent Linda Cardellini and a hilarious Anna Faris, who have minor, but attention-grabbing roles.

Ripped from the pages of Annie Proulx’s 1997 short story by the same name, “Brokeback Mountain” is artfully adapted by Pulitzer Prize-winner Larry McMurtry and his partner Diana Ossana, who translate Proulx’s sparse, elegiac prose into a divine cinematic language. Leitmotifs abound — the complex fragility and rigidity of social constraint, the elusiveness of satisfaction, the intense beauty of nature and the dangerous squalor of modern, mechanical life. Biblical allusions, symbolism and artistic shifts and transitions are not lost in the story’s new medium but instead become more subtle, more powerful.

Sound is also brilliantly employed: a few carefully placed horse grunts, the crunch of tires on gravel and an ambient, howling wind reverberate the entropic paths of the characters. The score and appropriate soundtrack work wonders, including Emmylou Harris’s doleful ballad “A Love That Will Never Grow Old,” which is itself as lachrymose as the film’s weepiest moments.

Nothing, though, astonishes more than the image-making power of cinematographer Rodrigo Prieto (“Amores Perros.”) His camera soars over the faux Wyoming landscape — the movie was actually filmed in Canada — then through the interiors of austere Middle America with clean precision. Instead of tricky, pretentious camera angles and techniques, Prieto opts for a series of enduring, postcard-perfect shots. Some of these, particularly the closing frame of strategically aligned clothing and wind-blown grass, can be called nothing less than sublime.

So many things could have gone wrong with this film, yet none do. The actors could have destroyed their roles with awkward, stereotypical mannerisms. Fortunately, they do not. The adapted screenplay could have transmogrified Proulx’s words into a buttoned-down cliché; but it is a work of art that rivals the original text. Sexual politics and an issue-pushing agenda could have stamped it as little more than propaganda, but “Brokeback” takes the high road by supplying social commentary only indirectly, and with no sacrifice to the art of the picture.