I’m a firm believer in the fact that what makes long fiction great is, in principle, what makes short fiction great (and note, I’m talking specifically about flash fiction, i.e., stories that are 1000 words or less.)
Both deal with characters who face problems that they are motivated to overcome. This, I think, is the core distinction between action and conflict. The planet Venus is full of action, but as far as I can tell, there is no conflict, because there are no stakes for anyone. Things change, but the change doesn’t affect anyone.
What about a piece of fiction describing a picture, for instance Saturn devouring his son? There is action inside the picture for sure, but still there is no conflict, because the mere act of describing the picture makes us take a detached point of view: someone is looking at it. What happens to this someone? Does he look at the picture, understand that time is fleeting and quit his job to travel the world? That might be a story, or the start to one. But as long as it is just description, the action in the picture is neutralized, sterilized as it were (to avoid this effect, you would have to describe it from the inside, showing Saturn as he chases his son, the son fleeing, etc.)
So yea, conflict. Short fiction has conflict in that it shows a character pursuing something and either succeeding or failing, or something in between. Or it may show a character facing a problem which forces a specific desire into the limelight. For instance, we don’t consciously desire to breathe, but if a character is drowning, then his or her desire for oxygen is pushed to the fore by the problem that they find themselves facing.
However, very short fiction, which is one of my favorite types of fiction, can’t afford some of the luxuries of longer stories, especially as it concerns character growth. You can absolutely show a character giving up a prejudice, for instance, after facing a problem, or becoming morally better or worse, but you still lack the type of gradual “character conversion” that you can afford when writing longer stuff, and you can’t delve deeply into the wherefores and whys.
I think that the reason flash fiction tends to have punchier twists is in order to make up for the constraints it is subject to compared to regular short stories or even novels. At the end of the day, in a story of 1000 words or less, your character is going to be little more than a stick figure even if you take great pains to add depth to him.
Case in point, my Dr. Johnson, from Why the Dead Stay Dead, which I published here some days ago. I tried to make him as 3D as the protagonist of a 997-word story can ever be, but there is a limit to what’s feasible. Same with some of O. Henry’s shorter stories. You remember the punchline more than the tidbits of characterization. I think there is nothing wrong with this feature of flash fiction. It is just a much more twist-based form of fiction and I appreciate it for that, especially considering that my longer fiction tends to be more heavily character-based.
In other words, while a character in a long story may be interesting in his own right, the protagonist of a very short story may have his charm, but at the end of the day he’s mainly a pair of eyes through which a conflict is carried out and a twist experienced. What makes him or her compelling is that they are adequate expressions of the story-problem.