The full quote...

  "No one could know Serling, or view or read his work, without recognizing his deep affection for humanity, his sympathetically enthusiastic curiosity about us, and his determination to enlarge our horizons by giving us a better understanding of ourselves. He dreamed of much for us, and demanded much of himself, perhaps more than was possible for either in this time and place. But it is that quality of dreams and demands that makes the ones like Rod Serling rare ...and always irreplaceable."

—Gene Roddenberry, in his eulogy at Serling's 1975 funeral