”There is a very special guest in the audience tonight,” said Siegfried, the blond half of Siegfried and Roy at The Mirage on July 10. ”An Oscar-nominated actress whose performances have moved us…”

Cathy Moriarty, the beautifully blowsy star of Raging Bull (Best Supporting Actress nomination, 1980), Soapdish, and Casper — and who happened to be seated next to this ENTERTAINMENT WEEKLY critic that night — slunk deep into the show-room banquette. ”I can’t believe he’s going to do this,” Moriarty growled. ”This is so embarrassing.” Siegfried extended his arms grandiosely in our general direction. Those of us lucky enough to be sitting with Moriarty straightened our posture, preparing to be doused by her spotlight.

Tension at the table mounted, until: ”Ladies and gentlemen,” said Siegfried, ”Miss Gloria Stuart!”

As Moriarty just sat there, either calmed down or let down, the 88-year-old Titanic star took a bow and a microphone and began expressing her appreciation for Siegfried & Roy’s artistry. And then expressing her appreciation for all the people who made it possible. And then expressing God knows what all; the woman can go on, and Siegfried seemed not quite sure how to get her to stop. Stuart was wearing a spangly little heart-shaped beauty mark decal on her cheek, which was enough to give me a giggle fit. Put off by such rudeness, Moriarty punched me in the arm — hard.

This incident, in a metaphorical nutshell, sums up a great deal of the current Vegas entertainment experience: magicians, tourists, quasi-name-brand celebrities, disappointment, a good laugh now and then, and not a little pain. And if the Vegas hotel-casino operators have a say in it, you’ll be having that experience soon. Despite the worried Asian economy, the glut of hotel rooms in Vegas — more than 105,000 by last count — is expected to increase by about 15,000 by the end of the millennium. Vegas wants you, and Vegas’ stages are considered a major untapped resource for keeping you happy. Casino mogul Steve Wynn and Hollywood producer-manager Sandy Gallin are planning to develop Broadway-caliber shows, and Peter Morton’s Hard Rock Hotel and Casino is catering to its young clientele with acts like Sheryl Crow and the Wallflowers. (Take a look at the new breed of Vegas tourist lounging by the Hard Rock pool — nubile hipsters hell-bent on disposing of income.) What, then, does this impending renaissance mean for the old-fashioned Vegas spectacle — the long-running comedy-variety shows installed in hotel show rooms long ago in order to lure gamblers? A quick tour through three shows from different Vegas genres — a spectacle, a star vehicle, and a T&A romp — reveal a very American art form (if you could call it that) at a crossroads.

It costs $89.35 per ticket to get a look at our first genre, represented by the two taut Teutonic titans of magic. I refer, of course, to Siegfried and Roy (The Mirage; 702-792-7777), though if you think you’re buying a magic show, think again. What you’re getting is pure Vegas-style spectacle. Siegfried spends much of the 95 minutes posing and gesturing amid a dense population of dancers; the chorus boys have big leonine hair, the girls are dressed, I think, as some kind of insect. There is much fog and fire, and Roy keeps popping up like a bad penny — from boxes, the back of the show room, etc. But the real star is the glorious parade of rare white tigers, all of whom pose as professionally as Siegfried, and one of whom is hoisted high … and then disappears! Whether this magnificent menagerie is worth the price of admission is up to you and your accountant. Siegfried & Roy are as slick and interesting as Wayne Newton’s hairdo, and they’re just about as hip. The face of Vegas is changing; it’s time Siegfried and Roy changed theirs. From the looks of them, this would not be an alien concept.

Speaking of hair, remember when David Cassidy’s cascaded past his shoulders and you thought Shirley Jones was the coolest mom in the whole world for allowing such a thing? Well, the hair is cut short, Cassidy is 48, and he’s Vegas’ resident former superstar — here to remind us (and this information will cost you at least $45 a ticket) that he’s still kicking, not to mention singing, leaping, and flying through the air in the monolithic, cast-of-thousands $45 million musical-variety show EFX (MGM Grand; 800-929-1111). Cassidy stars energetically as a busboy who takes a journey through his childhood imagination, bounding into the shoes of Houdini (magic tricks!), P.T. Barnum (trapeze artists!), and H.G. Wells (a 3-D time-travel movie! You can keep the glasses!). To call EFX a star vehicle is an understatement. It’s a star battleship; you may never see a live show this extravagant, which makes it somewhat important and a joy for the kids. But the show’s script makes The Partridge Family look like the Brontë sisters, and that makes EFX weirdly pornographic — so much to see, so little to think about, and after you’ve seen enough of it, your own boredom might surprise you. Until Cassidy starts pattering with the audience, shaking us awake with self-deprecating humor and a few topical jokes. The audience roars, free for the moment of empty glitz and common-denominator humor. Under Cassidy’s famous hair lies EFX‘s brain.

Then again, who goes to Vegas for brains? I, for one, was titillated by the town’s promise of south-of-the-neck entertainment. But while the signs on some shows say ”adults only,” they’re largely PG-rated affairs, many of them operating on the premise that audiences are still capable of lip-smacking over two bare breasts, even when their showgirl owner is otherwise covered in gowns by Bob Mackie wannabes and Teletubby headdresses. The T&A arena seems wide open for shows that can appeal to audiences born after 1955, and there is a new show that does just that: The History of Sex (Golden Nugget, 702-386-8100). Starring handsome Broadway vet Michael Gruber (Cats) and gorgeous Candace Davis (she paid her dues singing on Norwegian Cruise Lines, bless her heart), The History of Sex bounces through the titular topic, beginning with a nearly naked Adam and Eve and consistently — cleverly — objectifying with equal opportunity the 12 Fosse-esque whistle-worthy male and female dancers. In a retrofitted version of the Cole Porter ditty ”Let’s Do It, Let’s Fall in Love,” Gruber tells us that ”For cash a girl on the phone does it/George Michael all alone does it.” That’s smart stuff by Vegas standards, making the small-scale, unassuming History of Sex the best adult bet in town at $29.95 a ticket. This is not to say that Siegfried & Roy and David Cassidy should take their clothes off, but even Gloria Stuart might appreciate a good George Michael joke. Siegfried & Roy: B- EFX: B The History of Sex: B+