SYLVESTER Stallone's latest film, Cliffhanger opened in Hongkong at the weekend. Arnold Schwarzenegger's Last Action Hero opens on July 1. The battle of the brutes is about to begin. Here is how the new films are being billed. Cliffhanger: ''She was an inexperienced climber, she trusted him to rescue her, but something went wrong high above the valley floor, and Gabe Walker (Sylvester Stallone) has been blaming himself for her death ever since. ''Unable to deal with the tragedy, Gabe quit his job with the Rocky Mountain Rescue Team and fled from his once-cherished mountains, leaving behind his self-esteem, his friends and the woman he loves. ''Now he must return to those dreaded peaks, where he finds himself trapped in a desperate battle against ruthless criminals, unforgiving nature and himself.'' Last Action Hero: ''Steady, relentless, powerful . . . Sergeant Jack Slater (Arnold Schwarzenegger) has never lost a battle in the war against crime. ''Slater can dodge bullets effortlessly, survive tremendous explosions and take on an army of thugs single-handedly. Jack Slater is also the greatest fictional movie hero on the big screen. ''An otherwise invincible juggernaut, Slater's movie world gets shaken up when a magical ticket blasts 11-year-old Danny Madigan out of his theatre seat and into the movie.'' Stallone vs. Schwarzenegger. Fair contest? Maybe not. Arnold's cinematic fortunes obviously are in the ascendancy, Sly's in decline. While each has been named Star of the Year by the National Association of Theatre Owners, for Arnold the honour came in 1987, for Sly, in 1976. Earlier this year, the theatre owners named Schwarzenegger the international box office star of the decade. Schwarzenegger's last two films, Total Recall and Terminator 2 have, according to Variety, grossed more than US$100 million domestically. Stallone's last film, Stop! Or My Mom Will Shoot! has grossed only US$12 million, placing it down in 50th place (out of 152) for 1992 motion pictures. Schwarzenegger reportedly makes US$15 million a movie, Stallone US$6 to US$9 million. What's more, Arnold is going for the family trade. Last Action Hero, billed as a fantasy-action-adventure-comedy, is without graphic violence or strong language, while Cliffhanger contains an abundance of four-letter words. Has Arnold reformed? Parenthood, it is said, has softened him. He has estimated that he has killed 275 people on-screen, but also has observed, ''I think America has seen now enough of what violence has done in the cities.'' Initially, of course, both Arnold and Sly built reputations as killing machines, using old-fashioned muscle or high-tech weaponry. Take no prisoners, speak economically. A few years ago, though, they began to drift into comedies of sorts: Twins and Kindergarten Cop for Arnold, the doubly wretched Oscar and Stop! Or My Mom Will Shoot! for Sly. At one point Stallone even talked about playing his John Rambo character as an ecologist fighting for the environment, prompting writer-director Richard Brooks to crack, ''What's he gonna do? Shoot the vegetables?'' The appeal of both actors, besides their ability to shoot 'em up, blast 'em up, burn 'em up, could be that in their own lives they represent the American Dream. Stallone was born in New York's tough Hell's Kitchen. Arnold's family in Austria didn't have indoor plumbing, a telephone or a refrigerator until he was 14. Politically, Sly seems to have kept a low profile, but Arnold - dubbed Conan the Republican - often has been rumoured to be seeking the governorship of California, which he denies. Besides his screen persona, he is best known for having been chairman of the President's Council on Physical Fitness by George Bush. Arnold says of his Terminator role: ''Everyone would like to be a Terminator. Everyone would like to be a person who can take care of the job. Whoever makes you mad, you can get even.'' And Sly says of his Rambo image: ''People think I've got the IQ of a hockey score. I'm supposed to be this primordial being who slurs his way through life. My vocabulary is larger than 90 per cent of the writers I've met.'' SYLVESTER Stallone's latest film, Cliffhanger opened in Hongkong at the weekend. Arnold Schwarzenegger's Last Action Hero opens on July 1. The battle of the brutes is about to begin. Chicago Tribune.