Ordinarily one would expect that since the title character in Adam Sandler’s new comedy travels from hell to earth (several times, in fact), the audience would have to take a reverse cinematic journey. “Little Nicky”–at least for those well-disposed toward the star, who after all is an acquired taste–isn’t quite as bad as all that, but it isn’t terribly good, either. It’s one of those pictures that ought to be a lot funnier than it turns out to be; despite a lot of visual imagination and some sharp in-jokes and surprising cameos, it’s really a letdown after “Happy Gilmore,” “The Wedding Singer,” “The Waterboy” and “Big Daddy.” It may not be a celluloid hell, but it’s no heaven either. It’s right in the purgatorial middle. (It doesn’t even match the off-the-wall morbid charm of 1991’s “Bill and Ted’s Bogus Journey,” in which the underworld also played a prominent role.)

Sandler plays the younger son of Satan, a sweet but oafish sort with a scratchy voice and gargoylish appearance. When Dad, played by Harvey Keitel in horns and a dark jumpsuit, decides to extend his reign by a second thousand-year term, his nasty older sons, Adrian (Rhys Ifans) and Cassius (Tommy “Tiny” Lister, Jr.), who’d been planning on taking over Hades, escape to earth, which they plan to turn into a “New Hell” by encouraging people to sin with abandon. Since their departure freezes the fire-fountain that deposits the recently-departed for eternal torment, it endangers Satan’s survival: he threatens to decompose quickly unless they can be brought back. So Nicky is dispatched to earth to capture and return his siblings. In the ensuing extended chase, he’s aided by a lascivious, talking Bulldog named Beefy (voiced by Robert Smigel, the cartoonist from “Saturday Night Live”); gets romantically involved with a shy designer named Valerie (Patricia Arquette); and is befriended by two would-be disciples of the black arts, Peter and John (Peter Dante and Jonathan Loughran). An orgy of special effects and sketch-like comic episodes culminate in a final confrontation between Adrian and Nicky, the outcome of which is hardly in doubt.

What’s good about “Little Nicky” is that it exhibits a lot of stylistic exuberance (the look of hell is pretty amazing), and its allusions to other films and TV shows are affectionate and often amusing. (There’s an obligatory nod to “The Exorcist,” of course, but Sandler’s entire characterization is clearly based on Quasimodo, down to his line “I’m not a monster,” and among numerous other riffs there’s even a recollection of “The Zanti Misfits” episode from the original “Outer Limits” series in one of the more elaborate effects sequences.) As much as one might admire the level of invention apparent in all this, however, the unhappy truth is that most of the bits don’t come off, or at least fail to reach the level of hilarity they’re aiming for. A big set-piece at a Harlem Globetrotter’s game, for example, just lays there, and most of the “transformation” moments (the demons regularly “possess” people to do their bidding) are singularly uninteresting. Even Beefy, who’s no doubt intended to be the irresistibly droll canine companion, gets tiresome after awhile. A lot of the humor is crass and rude in typically Sandleresque fashion, of course, but that’s not what’s wrong with it; the problem that it’s mostly just flat (examples: maybe Allen Covert’s turn as Nicky’s roommate, who’s ostentatiously gay but denies the fact, and the sight of repeated punishments meted out to Hitler in hell could have been funny, but in each case the writing is so poor it’s demeaning instead).

The mediocre laugh-level isn’t for lack of trying; there’s a big, talented cast at work here, putting out lots of effort. But with a few exceptions, they don’t make much of an impression because their material is weak. Sandler himself hits the target at times, but his combination of nerdiness and lovability is only sporadically amusing, and some of his dopey ripostes are embarrassing. Arquette makes a pallid romantic interest, and Ifans doesn’t generate much fun as the lip-smackingly villainous Adrian (it’s a good thing that Lister, who’s even duller, disappears relatively quickly). Dante and Loughran, meanwhile, suggest far too successfully the cluelessness of the drug-impaired. There’s a raft of cameos by former SNL colleagues and others, but most of them (those by Dana Carvey, Kevin Nealon, Michael McKean, Quentin Tarantino, Lewis Arquette, and Carl Weathers, for example) are awfully lame; even more horrible, Clint Howard does a transvestite bit that couldn’t be worse, and Quentin Tarantino’s repeated appearances as a blind preacher are atrocious. In partial compensation, Keitel seems to be having a good time, Rodney Dangerfield bugs out his eyes amusingly as Granddaddy Devil Lucifer, and Jon Lovitz, Henry Winkler and Rob Schneider manage to be funny in their brief bits. Reese Witherspoon is momentarily enjoyable in a final twist that’s a takeoff on the Darth Vader motif from “Star Wars,” but once again, the idea is drawn out way beyond its shelf-life; and Ozzy Osbourne’s last-minute appearance is yet another instance of something that’s a pretty good idea but is poorly executed.

“Soon you will see things more horrible than you can even imagine,” the evil Adrian announces at one point in “Little Nicky.” He exaggerates; nothing in the picture is all that terrible, unless you’re allergic to the usual gross-out stuff and sniggering vulgarity. But while you have to admit that the flick is much more ambitious than any of Sandler’s previous efforts, the sad fact is that its reach exceeds its grasp. Its characters fly about periodically, but the movie itself never takes wing; despite the fact that parts of it are set in heaven and hell, the humor remains decidedly earthbound throughout.