It's hard to name just one feature, I have quite a few in mind that I wish every game had. As others have already mentioned: voiced mc, characters calling mc by her default name, flowcharts (especially for long games with many endings), love catch, and a skip to next choice button that doesn't lag lol. Two other features I wish were in every game are when the characters have blinking eyes and moving mouths, and also when we get the LI's POV so we know what he is thinking/feeling at certain and important moments in the game. I'm not sure if the second one is considered a feature that's being discussed here haha, but I decided to include it here anyways because it's something I've always loved in games.