In a

post on the Asimov’s forum, Gardner Dozois, inspired by a recent A&E or
History Channel poll, asked the question: "Who is ‘The Most Important
American’?"

He goes on to say: "Putting the emphasis on the word ‘American,’ I’ve come up
with three candidates, without whom there probably would be no America, as we
know it today."  They are:

(1) George Washington

(2) Abraham Lincoln

(3) Franklin Delano Roosevelt

Gardner explains his choices (see the

post for more details), and sums up by saying "So these are my candidates
for the title–since without them, for better or worse, America probably would
not have survived in its current incarnation long enough for them to be asking
this question on the History Channel in the first place."

All this leads to my inevitable follow-up questions:

(1) Who is "The Most Important Science Fiction/Fantasy Writer"? 

and

(2) Who is "The Most Important Science Fiction/Fantasy Editor"? 

Of which writers/editors could you say that without them, for better or
worse, SF probably would not have survived in its current incarnation long
enough for me to be asking this question?

Give your top three answers for each.  I cross-posted this to the F&SF
message board, so please post your responses there, under the thread titled "Who
is The Most Important…?"