I’ve been thinking of a quote from Gygax that appeared in something he wrote in Strategic review years ago: “…the major factor was always envisioned as the underworld adventure, while the wilderness trek assumed a secondary role, various other aspects took a third place…”
He was speaking of OD&D with this. I understand that more recent versions of the rules speak of three pillars, though they seem to be quite different from what’s mentioned in this article. (Note: I’ve no experience playing 3rd edition on, just know of things from reading discussions about them.)
For my purposes, this touches on games in the OSR, whether retroclones or not. An OSR game, I reckon, can be set out from others based on how it prioritizes the various possible focuses. While OD&D was primarily about the dungeon–underground exploration–another OSR game can focus on social interactions, foremost, another on something else. (3rd edition and later appears to have chosen combat as the primary focus of play.)
That leads to the question: what various focuses or pillars do you design for? Do you focus on one primarily?
It offers an easy answer to the question of “What does your game offer that D&D doesn’t?” (which I find kind of silly, in general). If you can identify what aspects of adventure or character or whatever your game deals with, and how your design prioritizes those things, you’ll gain a better understanding of what your game is and how to polish it.