To me, there's a very clear sign of good storytelling: it's the moment you feel something. I've read plenty of stories that I just sort of coasted through, blandly turning pages until I reached the end, and have walked away saying, "Eh, it was alright." But I've also read stories that had me yelling and turning pages fervently, draining each page of it's words so I could move onto the next, ravenous for the conclusion. To me, that's the difference.
There are some stories that just get to you. Where a character falls unexpectedly, and you feel tears welling up in your eyes. When someone is betrayed, and you read on, furious at what is transpiring. When the main character gets caught in a lie and you're terrified with them, scared to keep reading out of fear of another mistake that could cost them their lives, even though you know there are several more books in the series. These kinds of moments, and the stories that contain them, are what I consider good storytelling.
I remember being told over and over again as a kid that books are gateways into another world and that you could lose yourself in a good book. That's the basic standard I hold books to. Do I get lost? Do I get caught up? Do I cease to see the world around me, my living room fading into the deck of a ship in the middle of a choppy sea, watching as pirates battle to the last man? Or is the dialogue kinda bad and I'm very aware that I'm reading a book, openly scoffing at the authors choice of phrasing, completely out of sync with the story? I want to be lost. I want to read a book that sweeps me up so entirely I create memories of the books moments. I want vivid images in my head of things that have never truly happened. I want, more than anything to feel all the joy, anger, and pain of every character I read about.
I knew someone who said they hated sad endings because they got bummed about it. I never understood that. If I walked away from a book sad at something that had transpired... hadn't the book done its job? Sure, I might be morose, and that's never a fun time, but... if that was what intended by the author, it always leaves me feeling more connected to the story, and the characters within.
I'm currently reading a story about thieves trying to lie and connive their ways into fortunes that are all but impossible to grasp. Every lie the characters make has serious ramifications for the future, and the slightest slip ups have dire consequences for them, namely death. Earlier while reading, a character had made the decision to drop the ruse he had been building for two full years, in order to come clean to someone and try to gain their trust. My hands were shaking reading the passages. What if the woman he was speaking with didn't understand what he was trying to achieve? What if she thought him a threat? Would that be the end? What if someone else had already told her, blowing his entire plan out of the water? What if... he lied again? Digging himself into a deeper hole? All these questions drove me to read more and more, desperate to know what would happen, and terrified that it would all go to complete shit. It's an amazing story, one that has me fully griped. One that has me so invested in the characters that I'm terrified for them, afraid of all those who would do them harm, but also overjoyed when their schemes succeed.
Maybe I've meandered a bit here and there, but I hope I've made my points.... somewhat clear. I've always been a terrible hand at essay style writing. S'why I usually stick to wizards and monsters. Much easier to write about them. To sort of... sum up here, I think the mark of a good story is one that makes you feel something, whether it be joy or anger, or what have you. If you get to a point where you care enough about the characters that you're afraid for them, cry with them, and hope with them... then someone did something right.
In my writing, that's all I ever strive for. Can I get them attached enough to feel anger over what's coming in the story? If this character dies... will someone reading it cry? If I can achieve any of that, I've done well. But I could do better. And the writing continues.