Hollywood must specialize in Faustian bargains. There’s simply too much evidence walking around to deduce otherwise. Consider the once-interesting Brendan Fraser, who now plays second banana to the special effects in “Mummy” movies. Or Scarlett Johansson, mousy and introspective in “Lost in Translation,” now brassy, blowsy and bleach blond. Once upon a time, Whoopi Goldberg won an Oscar. Once upon a time, Chevy Chase was funny.

And then there’s Nicolas Cage.

Let us ask ourselves something: Why is Nicolas Cage a movie star? And why do we care?

The answer, in part, is that Cage — whose latest, “Knowing,” opened Friday — won an Oscar in 1996 for playing a suicidal alcoholic in “Leaving Las Vegas,” a gritty, brutal, honest movie, wonderfully acted (by both Cage and Elisabeth Shue) and which confirmed what a lot of people had long believed: that Cage was the most interesting actor in American movies.

His performance in “Raising Arizona” remains iconic. Likewise, “Wild at Heart.” From the time he was 17 — and got passed over for the Judge Reinhold role in “Fast Times at Ridgemont High” — he was cutting a righteous swath across the screen, in movies that rarely missed such as “Valley Girl” and “Birdy.” He even made an impression in some pretty dubious projects, including two directed by his uncle Francis (Coppola), namely “Cotton Club” and “Peggy Sue Got Married.” Then the Coens cast him in “Raising Arizona.” He became Cher’s one-handed romantic poet in “Moonstruck.” That was followed by “Vampire’s Kiss,” the immortal “Wild at Heart” and a mixed bag of principal roles leading up to director Mike Figgis and “Leaving Las Vegas.”

What happened then bears the infernal reek of sulfur, brimstone and gross receipts. “Con Air,” in which Cage played an unjustly convicted parolee battling a planeload of criminal misfits and psychopaths, was an action thriller — the old adrenaline-fueled thrill ride/riveting roller coaster of a big old movie. Yes, Cage had appeared in “The Rock” immediately after winning his Best Actor statuette (thus abandoning idiosyncratic leading manhood forever), but it was “Con Air” that made Cage fans sit up and say “Wha . . . ???” (Significantly, Steve Buscemi was in the movie, too, sliding into the Beloved Character Actor slot that Cage was so busily abandoning, in a flick that was about as cynically brainless as anything in the history of mall movies.)

And so it has been, with few detours from the action star/blockbuster track upon which Cage has trod with particularly graceless aplomb, and virtually no humor at all, except on top of his head, where his hair is continual source of mirth and mystery, because you never know what it’s going to do, where it’s going to go or to whom it once belonged. Some favorites: the punky cut of “Ghost Rider” (2007), with its black spikes and bangs; the inky-looking Franz Liszt arrangement of last year’s bewildering “Bangkok Dangerous.” Or the gravity-defying-do of “Lord of War” (2005), which was Cage’s best performance in years, because it returned him to a realm of moral ambiguity and outsider status, precisely where his talent thrives — rather than as a low-rent Indiana Jones (“National Treasure”), a thoroughly unconvincing Italian lover (“Captain Corelli’s Mandolin”) or anyone named Memphis Raines (“Gone in Sixty Seconds”).

Taking on preposterous roles, like the supposedly coldblooded hit man of “Bangkok Dangerous” (“My name is Joe. . . . This is what I do . . .”), it’s clear that Cage would like to assume the mantle of Clint Eastwood. His character is a man of few words, he grimaces with irony-free disgust at the moral bottom-feeders of the world and he dispenses large-caliber justice. But Cage has never taken Dirty Harry’s advice: A man’s got to know his limitations. Cage isn’t a sex symbol and — stripped of the existential complexity of his early roles — he’s not that interesting to watch. Despite the fact that there are Nicolas Cage action figures available, watching his pursuit of action stardom has been like watching a Jack Russell terrier romance a Doberman.

But in an industry, and a town, where a movie is judged entirely by its profits, Cage is secure. “National Treasure: Book of Secrets” made more than $450 million worldwide, its predecessor, $348 million. “Gone in Sixty Seconds” made more internationally ($135 million) than domestically ($102 million). These are not the kind of figures that prompt a man to resume playing suicidal alcoholics. “Ghost Rider” probably made less money than people might have expected — $116 million here, $113 million there, according to boxofficemojo.com.

Does the average moviegoer care how much money Nicolas Cage makes? Probably more than he or she should; given the celebrity-besotted culture we live in, it’s inevitable. But it seems the unavoidable conclusion that Cage, once held up as an example of the intrepid artistic impulse, has become something of the poster boy for blind ambition, cynical role selection, questionable judgment and, worst of all, humorlessness: He glowers, he hunches, he looks meaningfully into the distance without it meaning anything at all.

If Cage were replaced tomorrow by Ben Stiller, we’d get all of the above plus a couple of laughs. Instead, we have an actor who used to be able to do something remarkable — overcome a lack of native charm by embracing his inner outsider, creating affectionate portraits of unlikely heroes, and soldiering on despite a seemingly unmerciful universe. It may not pay as well. But that’s a Nic Cage we could use.