For those of you who dont know, Landau was considered for the role of Spock but turned the role down before it went to Leonard Nimoy. Or so its been said. From what I've heard Gene Roddenberry had wanted Nimoy from the beginning. But Landau as Spock would have been interesting.
That would have been.... odd. He would have pulled off the solemn nature of Spock but I don't know if he would have had the depth and odd charm. Landeau was known for cold, edgy characters. It remind me of Midnight Cowboy. They almost cast Michael Sarrazin in the role of Joe Buck, Jon Voight's character. The person who cast the film literally put her entire career on the line and did everything she could to sabotage the production until she could get Voight from NY for a screen test. When you think of how groundbreaking that film was, who other than Voight could pull off the redneck "Aw, Shucks" male prostitute? You just can't see anybody else in that role. It's like that for Nimoy and Spock.
Martin Landau had that smooth voice and could play a villain to good joe. RIP and condolences to his family and friends.