"A River Runs Through It," starring Brad Pitt, is flowing past all the rental competition, but can't quite catch up to top-ranked "The Distinguished Gentleman," settling for second. "River's" run is impressive considering it's the kind of slow, rural drama considered a questionable rental attraction, despite its big box-office numbers. Yet many video retailers, using theatrical gross as a gauge, stocked up on it heavily anyway--and they were right. Some retailers in urban areas report that "River" is their top rental. The British drama "Howards End" is doing good business too (No. 9) in its second week on the chart. All those Oscar nominations--including best picture--and Emma Thompson's triumph in the best actress category, drew attention to the film. Despite all the acclaim, many fans perceived it as a snail-paced English drama, so its box-office take, $22.9 million, is relatively small for a big award winner. But audiences have a greater tolerance for "difficult-to-watch" movies on video, so this one should continue to do just fine as a rental.