Nearly 4000 posts. Yey!
Back on topic, here are my 2 cents.
When we say 'the best car in the world' - what attributes of the car are we talking about? Is it performance? Is it reliability? Is it luxury? Is it about pushing the technological boundaries forward? (This IS what S Klasse is all about

) Is it the something intrinsic, call it aura, that surrounds the car?
All things considered, S Klasse probably was, and still is, the best car in the world. But one cannot simply compare it with Bentley/RR, because those cars are not about
all things considered, they are about aura, splashing the money, having
ultra-luxury toy. This is something S Klasse lacks, simply because it is not about it.
Now, you also have to bear in mind that B/RR are sold and seen on the street in much, much less numbers than S klasse, AND Mercedes-Benz cars in general. Back in the 60's, MB had much bigger
cachet then today. Something which is very important in this category. My guess is, Pullman will be fantastic car. But it has to be completely different visually from the S Klasse, or it will have same destiny as Maybach did, if it wants to compete with B and RR (Mulsanne and Phantom, to be clear).