Rick wrote:
It's really hard to quantify such nebulous things (Most Popular?  Most Famous?  Sez who?).  But my feeling is, that, during Bill's time-frame of late 40s, early 50s, Ray Bradbury would have been the most famous LIVING sf writer.  But that's just a feeling.
Which was my point.  Bradbury was also famous world-wide; his works were translated into many languages.  He was especially popular in France, which sort of puzzled him; he concluded (to me, at least) that his style must work really well in French.  He was also the most popular contemporary non-Russian writer in Soviet Russia--which made him not a single ruble, since at the time (and maybe still, for all I know) Russia did not subscribe to any international copyright treaties or whatever.  They didn't pay Bradbury or any other American writer for publishing their works.  But as I say, he was extremely popular in Russia.
  
I don't know what they made of IT CAME FROM OUTER SPACE.  Maybe balalaika picks.