Monsterpal wrote:
I'm still going with Heinlein, "The Dean of Science Fiction Writers."
We aren't talking about their quality as a writer, or their popularity amongst sci-fi fans.  We're talking about general fame.  Does the general public--outside of sci-fi fans--really know who Heinlein is?  Bradbury's has his work endlessly adapted on radio, television (including a series with his name in the title), movies and in comics; he's has probably hundreds of essays and interviews in mainstream publications; and he's been interviewed on televsion many times.

By contrast, Heinlein has only had a few works adapted, and I can't recall ever seeing him interviewed on television or in a mainstream publication about anything. (The IMDB doesn't list any credits for Heinlein as "self", versus 75 for Bradbury, and that's almost certainly not including appearances on various news programs and local shows.)

Arthur C. Clarke became famous to the world as the co-writer of one of the most famous and acclaimed science fiction movies of all time, and also had a TV show or two with his name in the title.  Isaac Asimov also contributed many articles to mainstream publications and was interviewed on popular TV shows like David Frost (4 times) and Dick Cavett.  By comparison, Heinlein may as well have been a hermit living in a cave.  Sure, every sci-fi fan knew his name, but the general public?  To them he was more like "Robert who?" 

Yeah, Bradbury was so famous and popular, I see that ol' familiar name on the marquee to draw in the crowds: RICHARD CARLSON.

In IT's screen credits, SCREENPLAY BY HARRY ESSEX is large, and under it, like a forgotten footnote, is STORY BY RAY BRADBURY, in Aubrey Wisberg-Jack Pollexfen-worthy small print.  

On the other hadn, Tom, try taking a look at that BEAST FROM 20,000 FATHOMS poster (released the same year) that proudly declares "Suggested by the sensational SATURDAY EVENING POST story by Ray Bradbury."  Warners clearly saw publicity value in his name, even if Universal didn't. (I would also argue that this was the start of his acheiving fame, and that he became much more famous as the years went by.)

As for Stan Lee or Rod Serling as candidates . . . well, they're certainly both quite famous, but I thought we were talking about prose fiction writers of short stories and novels, not broadening it to other media like comic books or televsion. (Serling did write some short fiction, but it was both awful and unsuccessful.)

Philip K. Dick?  I'd count him as a contender, as he's been getting more and more attention as a so-called "serious" writer as the years go by.  Dean Koontz?  Maybe, although many people lump him in with Stephen King as a "horror writer" rather than a "science fiction writer." (I'm not saying they're right or wrong, just commenting on how many perceive him.  Of course, if we count King as a science fiction writer--several of his works qualify--he's probably the winner, hands down.)

Vonnegut?  Excellent choice, and certainly a contender for the "most famous" title--although some snobs would probably object to calling him a science fiction writer, because they still think that a "serious" writer cannot be a "science fiction writer."