I've been reading Isaac Asimov's two-book autobiography. The first book of the series is In Memory Yet Green. I'm currently at 1941, when he was 21 years old.
Asimov wrote his classic short story "Nightfall" in 1941. It's about what happens on a planet where night rarely comes, because there are several suns. On several occasions, science fiction fans have voted for "Nightfall" as their favorite science fiction short story (not just their favorite Asimov story).
But Asimov had other favorites:
My own three favorite short stories are, in order: (1) "The Last Question," (2) "The Bicentennial Man," and (3) "The Ugly Little Boy."
Source: In Memory Yet Green, page 296
I haven't read all of Asimov's science fiction short stories, but of those I have read, "The Last Question" is definitely memorable.
Photo Credit: The photo of Heinlein, Sprague de Camp and Asimov is a work of a sailor or employee of the U.S. Navy, taken or made as part of that person's official duties. As a work of the U.S. federal government, the image is in the public domain.