So I've been playing Dark Souls II and it's gotten me thinking about the things that video games do really well. Two things I particularly like, and that the Souls games do extremely well, are crafting mechanics and teaching about the game through play. I will post about those in the near future, and maybe another new class. Right now though, I want to talk about side quests.
Now admittedly, side quests - especially fetch quests - can be really boring. See, for example, most of the Legend of Zelda side quests in recent years. But if done well, they can give a glimpse of the larger world. In Dark Souls I, there was that stuff with the golden crystal golem and her dad. Without going into too much detail, that side quest offers a sense of the reality of these characters. It doesn't feel like they exist for your benefit (like characters in video games so often do), but you get a glimpse at what the lives of people are like in a world of insane undead. Side quests provide take people or things that are sort of unexplained in the game, and provide explanations through interacting with optional game elements. They also can provide a sense of how individuals interact with one another and the world around them, and can drive conflict.
Side quests are also fun because they can drive play. I don't play the Elder Scrolls games, but my understanding is that a large part of the appeal is the ability to advance through a series of related side quests to become the head of a thieves' guild or church or whatever. This provides a degree of purpose in a sandbox setting, which allows players to measure progress and prevents stagnation of interest.
So. Side quests work particularly well in video games, because there is also the main quest that drives play. I don't think side quests would work so well in a sandbox or hexcrawl style tabletop game. Often as not there is no "main quest" for there to be side quests of, so side quests would be more just like a GM giving a "dungeon of the week" mission.
But for megadungeons, I think they work really well. Because megadungeons are both expansive and condensed, it is possible to travel between two extremely different locales (the elemental floor and the technology floor!) much quicker than it is possible to do this with hexing. Also, the players are less likely to have a specific notion in mind of where they're going. I mean, yeah, "down." But it's easier to know you're heading to the eastern city than it is to know you're heading toward the stairs that are probably around here, somewhere. This type of setting means you can have lots of side quests that don't look similar at all, all within a condensed area. You can have completely optional sidequests to find the mushrooms in area X, kill the beast in area Y, rescue the hostages from faction Z, and these can all be within reach immediately, in completely different regions, without feeling shoehorned. And with the notable exception of +Numenhalla, I can't name off the top of my head any dungeons that really use or encourage side quests.
So, yeah. People should use side quests more. If I am totally wrong or if you have a good example of dungeons with side quests, let me know.