The biggest winner at Hollywood Park Saturday was the Breeders' Cup itself.Although it had been the object of considerable criticism and second-guessing within racing this year, this Breeders' Cup was surely one of the most exciting, spectacular days of racing ever presented anywhere.

When trainers, jockeys and journalists watched the reruns of the races at a breakfast Sunday morning, even the most jaded felt chills and goose bumps as they saw Theatrical outduel Trempolino in the $2 million Turf, and then saw Ferdinand hit the wire a fraction of an inch in front of Alysheba in the $3 million Classic.

"It should have been a dead heat," Ferdinand's jockey Bill Shoemaker said, gracefully. "They're both such great horses."

Jack Van Berg, the trainer of the loser, couldn't have agreed more. He had lost tough photo finishes with Gate Dancer in two of the three previous runnings of the world's richest race. "When Gate Dancer was retired," Van Berg said, "they printed a brochure that said he was two heads away from being a legend. Well, now I'm three noses from being out of debt."

Yet even after this excruciating defeat, Van Berg couldn't suppress his appreciation for the drama or the success of the whole event. "The Breeders' Cup," he said, "is the greatest thing that's ever happened to this sport."

Much of the criticism of this Breeders' Cup had been directed at the choice of a California track as its site for the third time in four years. While California-based stables did win four of the seven events, the races were fair and honest. Even when the local filly Very Subtle upset New York's highly acclaimed sprinter Groovy, there was no home-court advantage involved. Groovy had been winning races without having to cope with the kind of raw speed that he faced in the Sprint; Very Subtle was faster -- and would have won their duel anywhere.

The Hollywood track did favor speed horses, although not so much that any undeserving horses won. (Tired front-runners did hold on much longer than they might have elsewhere, as in the Classic, where Judge Angelucci was only 1 1/4 lengths behind Ferdinand at the finish.) Given the tendency of the track, one notable losing effort was the one delivered by Regal Classic in the Juvenile. Rallying from 11th to finish second behind Success Express, the Canadian colt gave evidence that he could be a major factor in America's Triple Crown series next year.

One of the most heartening aspects of the day's events, to Breeders' Cup officials, was the performance of foreign horses in the two grass races. When the English superstar Dancing Brave ran so dismally last year, there was speculation that his loss would keep other European horses from making this trip. But top-class foreigners did come. Trempolino ran an excellent race in the Turf, and was simply beaten by a better horse; Miesque delivered a smashing performance to win the Mile in course-record time. Her managers announced Sunday that she would be kept in training next year and aimed principally for the 1988 Breeders' Cup at Churchill Downs.

The biggest losers at Hollywood Saturday might have been the horses who didn't show up. Forty Niner had been considered the leading 2-year-old in the country, but he skipped the Breeders' Cup -- part of the apparent boycott of the event by some haughty Eastern stables. After Success Express won here so impressively, running a mile in 1:35 1/5, Forty Niner might have blown the Eclipse Award by staying home.

The year-end championships were a major topic of conversation. Should Success Express or Forty Niner be the champion 2-year-old? Should Theatrical be named the champion turf horse over Manila, the brilliant star whose career was cut short by injury? Does Groovy or Very Subtle deserve the sprinting title?

And, most important, who is the horse of the year? Ferdinand? Theatrical? Alysheba? This will be the subject of considerable argument in the weeks ahead, but for now people who love the game can savor the memory of one of racing's greatest days.