HOLLYWOOD film companies have more than one good reason to celebrate the holiday season. Not only have several high-budget films performed well at the box office, but optimism runs high that others will find favor with the public."The entire industry was watching the Christmas pictures to find out whether the movie business still exists," says Thom Mount, a former head of Universal Pictures and now president of The Mount Group. "We were one nervous bunch. "The good news is that we have had five bona fide hits for the Christmas season so far, and we may get two or three more." Industry leaders, with a number of very expensive productions and fierce competition on their hands, had been apprehensive about the prospects: The box-office take declined by better than four percent during the second half of 1991. Added to this was the realization that many of the new movies on which the studios pinned their hopes had been brought in on astronomically high budgets, carrying with them the need for outstanding business to turn a profit. "Hook," the Steven Spielberg epic, for instance, cost $70 million, to which has to be added the high cost of marketing the movie. According to industry sources, the picture will have to earn well over $200 million before it can begin to show a profit. By way of comparison, "Terminator 2," the Arnold Schwarzenegger action film, released during the Thanksgiving period, took in well over $200 million during its first few weeks of release. The big Christmas attractions that have done extremely well at the box office include: "Cape Fear," directed by Martin Scorcese and starring Robert De Niro; Disney's animated "Beauty and the Beast,Star Trek VI - The Undiscovered Country,My Girl," starring Macaulay Culkin of "Home Alone" fame, and "The Addams Family," based on the popular Charles Addams cartoons and - loosely - on the 1964-66 sitcom. Anjelica Huston and Raul Julia, as Morticia and her romantically inclined husband Gomez, star. Still to be counted are Oliver Stone's provocative "JFK;" Barbra Streisand's "The Prince of Tides;" and Tom Berenger in "At Play in the Fields of the Lord." Interest also centers on Warren Beatty's "Bugsy," another film rumored to be in the $50-million budget range. "The depth of the depression we experienced last summer and fall was very shocking to the film business which prides itself on being recession-proof," says Greg Morrison, president of marketing for MGM. "More than the usual anxiety is attached to every opening of a big film because so much is at stake." Morrison points out that Hollywood's Christmas season in the past had started a week or two prior to the holiday, and that the practice of opening major pictures at Thanksgiving was new. "We didn't realize that Thanksgiving could be a potential gold mine for us." Industry executives freely acknowledge that the trend toward mega-buck budgets during the past two years has sharply increased the risk factor. They also emphasize that, in the light of the disappointing box-office receipts, serious efforts are underway to control production costs. Mike Medavoy, production chief at Tri-Star, a unit of Columbia Pictures, recently said that film budgets would come down by about $5 million. Paramount Pictures has let it be known that its average budget for major films would be reduced from $30 million to $20 million. "There is cost cutting everywhere in Hollywood today," Mr. Mount says. "The studios are realizing that they are better off developing their own screenplays rather than buying packages from the outside. From the studio point of view, when you have a good screenplay, the battle is half won, and the stars and directors come your way. You will see a much greater emphasis on scripts and internal development during 1992." The current euphoria is not uniformly shared. "We need pictures with 'Velcro' quality, films that have a definite hook to them," Mr. Morrison notes. "The climb-out from the conditions of earlier this year isn't going to happen overnight. "We may bask in our Christmas glory, and it may well extend into January, but we can't afford to ignore economic conditions, the competition we face from home video, and the vastly expanded number of screens available today. Also, it is costing us so much more these days to advertise and promote our movies. Like it or not, audiences have become much more selective, and we better keep this in mind when we choose our material," Morrison says. It should be noted that, neither in theme nor in substance did the Christmas lineup differ significantly from subjects treated by Hollywood in the past. "Hook" is a retelling of an old familiar tale; "Star Trek" essentially carries forward the same crew; "Bugsy" returns to the gangster theme; the "Terminator 2" sequel cashes in on a well-established formula, and "Cape Fear" is a remake - a very skillful one, but still a remake. Even "Beauty and the Beast," while critically acclaimed, offers what Disney h as always offered. While an expensive Hollywood picture depends heavily on the United States domestic market to recoup, industry executives point out that the vast international field is growing. Jack Valenti, president of the Motion Pictures Association of America, recently estimated that 40 percent of the US movie business's income today is derived from the foreign market.