A callback to this ooold post: here
For Pilgrims to Ruin
1. Subject matter: I think "quests" are fundamentally stories about self discovery, and that self discovery can only come through pain, when we make decisions about moving on or sticking to our guns. Growing up means suffering, learning means corruption. Innocence=Beauty, Experience=Ruin. This, I think, meshes well with stories about psychological horror in the style of Silent Hill and "wishmaker" stories like Stalker. Both feature abandoned, once civilised, but now ruined locales (call them allegories), which can also be found in the Prince of Persia. In my head, it all fits together.
2. Roleplaying as a practice: The conflict isn't really with the outside, but in the character's heart. For this kind of story the GM doesn't have to do anything really, only describe, the players are rolling against themselves.
3. Real, live human nature: I think this ties back into point 1. If you want something, there is a price. Everything has a price. Otherwise you can live on in your safe little cocoon, hidden from everything. If you WANT something, you'll pay for it. (so in game: Want=>Roll=>Pay=>Roll=>Pay=>Roll...)
For Sagas of the Icelanders
1. Subject matter: I think the frontier and the settlement of a savage, empty land can serve well to bring out essential human conflicts, in the tradition of the best tragedies. It can also serve as an exploration of how Christianity was gradually accepted. Plus, hey, it's goddamn vikings.
2. Roleplaying as a practice: I think every bit of the game should drive things to a bloody confrontation, the crux being the hard choice: to hold on and let it all fall apart or go into terrifying new directions.
3. Real, live human nature: I think we are all torn between tradition and radicalism. When neither is the obviously right choice, where do we ultimately turn?