The first two seasons of Mission: Impossible, with Landau and his then-partner Barbara Bain as recurring characters, were rarely less than good.
But the THIRD season, where Landau and Bain were pretty much the stars of the show even though Peter Graves got top billing, is IMHO some of the very best prime-time television ever made!
Not to disrespect Graves, or Greg Morris -- may they, too, rest in peace -- or Peter Lupus, but when certain Paramount Pictures executives took a dislike to Landau & Bain during contract renegotiations, they pretty much doomed the show to mediocrity, even if it did run 4 more full seasons.
Of course, there was much more to Mr. Landau than just M:I, but without M:I s3, the entire spy/international-intrigue genre would have been of much, much lesser quality in the decades since.
Thank you for all those hours of superior entertainment, Mr. Landau. Eternal peace and joy to you up in heaven.