The most compelling open worlds are the ones that feel like they would exist even if you never visited them, and the key to that illusion is to fill the world with convincing people. I'm not talking about the main characters, the quest-givers, or the speech-makers. I'm talking about everyone else—the background extras that fill the gaps in the world, the ones you tend to barely notice unless you slow down and start paying attention to them.
Early in my life as Arthur Morgan in Red Dead Redemption 2, I came across a woman being abducted. After killing her kidnapper and cutting her ropes, she thanked me and told me she was going back home. She climbed onto the dead man's horse, then rode off. I followed her—not in a creepy way, I swear. I was just curious if she'd really go home, or if the game intended for her to just ride out of sight and de-spawn once I stopped watching.
I tailed her for a long time as she rode over hills and through forests, until she came to a town, turned down a few roads, then dismounted and walked into a house. I can't say for sure it was really her house, but the illusion at least held up to my scrutiny.
I started following a lot of NPCs around, and not just ones I saved from kidnappers, but anyone who seemed interesting. I'd follow farmers around as they worked, carrying grain sacks and hay bales, examining livestock and jotting down notes, loading and unloading wagons. I love finding hunters out in the wild, who tell me to keep quiet when I ride over to them so I don't spook their prey. I follow them in a crouch, watch as they track their target, and then skin whatever they've killed before riding off again.
Even just hanging around in a town can be rewarding. One day in Blackwater gusts of wind were driving huge clouds of dust through the town, and many of the locals commented on the windy weather. If you misbehave and get into a gunfight with the local cops, the townsfolk remember that, too, chastising you about your behaviour the next time you visit. These may be randomly generated NPCs with no names and only a few lines of dialogue, but they still manage to feel real and persistent.
Where's the morgue?
Speaking of misbehaving, after a big noisy gunfight at Hanging Dog Ranch, a posse showed up to investigate and I bravely hid in the barn until I lost my wanted level. When I wandered innocently back outside—gosh, what happened here?—I saw lawmen loading the corpses onto their horses. I tailed one to see where he took it, though I lost him when a thunderstorm rolled in and I got attacked by a bear. After another gunfight, this one at Ridgewood Farm, I again tailed the posse to see where they'd bring the bodies they carted off. After long minutes of following, I got attacked and killed by some bounty hunters. Someday I'll figure out where they take all those corpses I keep piling up!
These minor characters aren't made perfectly, of course. I rescued a man from some bandits after his wife flagged me down on the road. After I killed the bandits and untied the man, he thanked me and said he was going to find his wife, who had run off. So I followed him, hoping to see their reunion. He just sort of rode around on trails for a while, but at one point when I got close to him he suddenly turned and said, “Do I know you?” Well, yes, you do, I shot two men in the face to save you five minutes ago. But he seemed to have forgotten me, and possibly forgotten his wife, too, their marriage the victim of a script that ended before they could reunite.
That's OK, though. Even if they don't always lead me somewhere interesting, I still really enjoy following Red Dead Redemption 2's NPCs around. They make the world feel less like a beautiful painting and more like a real place.