Elvis' 1968 comeback special is widely and accurately considered to be one of the landmark moments in rock history. Although it should be noted that a growing number of people, including Dave Marsh and Sheila O'Malley, have argued that it wasn't a comeback at all - that Elvis in fact was pretty damn great even during those years (generally, the era known as the "movie years") that others have disaparaged.
But one thing I think we can all agree on is that the segment of the show when Elvis sat down with his buddies and a guitar, and then proceeded to crank out some of the most memorable music heard in the last 50 years, is simply without precedent or peer in the annals of rock history. This was history being made before our very eyes - this was Elvis demonstrating to the world that yes, since his earlier peak there had been the Beatles, and the Stones, and Dylan, etc...but that it would not be wise to forget about Elvis. Because there were things that Elvis could do that no one could do then, or now.
So within that context, enjoy the King, with one of his two greatest Christmas songs - "Blue Christmas."