>Two vintage series are reprised this week. On Return to Green Acres (CBS, Fri., May 18, 9 P.M. ET), Eddie Albert and Eva Gabor must save Hooterville from developers. Pat Buttram, Frank Cady, Alvy Moore and other cast members from the '60s rusticom come back for a reunion that is, if possible, even more flat and dopey than the original. On Sunday, that burly barrister Perry Mason (Raymond Burr) is dusted off for another entertaining outing, The Case of the Silenced Singer (NBC, May 20, 9 P.M. ET). Guest stars include Vanessa Williams
, Tim Reid, Kene Holliday, Rex Smith, Alan Rachins and Nia Peeples.