LOS ANGELES, Dec. 19 - Are movies growing bigger as theater audiences are becoming smaller? That's one conclusion to draw from the box-office results of 2004, as Hollywood pursued its penchant for big-budget event films - from Warner Brothers' "Troy" to 20th Century Fox's "I, Robot," to Sony Pictures' "Spider-Man 2" - but the number of moviegoers in the United States dropped for the second year in a row. With nearly two weeks to go before the end of 2004, domestic box-office receipts appeared likely to top last year's total of $9.27 billion, nearing $9.4 billion, according to Exhibitor Relations,...