Let the Games Begin: Paramount's espionage thriller, "Patriot Games" with Harrison Ford, scored nearly $20 million its opening weekend, according to estimates by industry sources. It was the second largest opening of the year after the record-setting "Lethal Weapon 3," which earned $33.2 million during the May 15 weekend. This last weekend, "Lethal Weapon 3" did about $9 million in business and surpassed the $100-million mark in only three weeks of release. Disney's Touchstone Pictures' "Sister Act," starring Whoopi Goldberg, took in about $11.5 million for second place. Meanwhile, box office continued to fall rapidly for "Far and Away," which grossed about $5.7 million, and for "Alien 3," which grossed an estimated $4 million. Weekend box-office figures will be released today.