Ballyhooed 'Showgirls' Does a Bellyflop

REMEMBER ''Showgirls,'' the sexually explicit movie that got all the media hype? Critics called it pornographic. But Hollywood poured $40 million into it. Moguls hoped the slickly produced film would break down barriers to X-type movies in America's suburban malls.

After a strong opening weekend in September, however, revenues plunged. By its fifth week, the film had dropped off the Top-20 list. So far, ''Showgirls'' has recouped only about half its original cost.

Jack Valenti, president of the Motion Picture Association of America (MPAA), said before ''Showgirls'' debuted: ''If you make a movie that a lot of people want to see, no rating will hurt you. But if you make a movie few people want to see, no rating will help you.''

''Showgirls'' was rated NC-17 (the successor to ''X'') by MPAA.

Now Mr. Valenti says: '' 'Showgirls' wasn't a good picture ... because it wasn't entertaining.''

Travis Reid, executive vice president of Sony Theaters in New York, says: ''The marketing campaign was more effective than the film.''

Jane Brown, a media professor at the University of North Carolina, suggests that the film's failure shows that ''the American public have better sense than they are usually given credit for.''