I think I pretty much told you what those qualities were in my mind. Not everyone has to have an in depth backstory cuz not everyone in life has an in depth backstory. But everyone does have a life. And considering what im looking for in Elder Scrolls games, i want NPC's to have a life, not just be randomly generated space fillers. Thus i want my NPC's to have homes, schedules, jobs, possessions, etc. So yea i can go into Imperial City and only see a few dozen people, but they all have a home, a schedule, and something that they do even if its not much. Much better than a bunch of randomly generated space fillers that have no home or place where they belong and just aimlessly roam for the same of filling the streets. The quality of NPC's makes the city feel more "alive" to me than just a thousand random NPC's that do absolutely nothing.
Please go to your nearest Walmart. If you find 15 people there you are playing Elder Scrolls.
These 15 people have in depth back stories to them.
One of them is a father of 20, but his children are nowhere to be found. (You'd think 20 children are a hard thing to miss)
One of them lost his arm in the great Crusader Dagon Akatoshian Superhero Wars.
One of them is called Andrew and tells you what a great place Walmart is.
One will invite you into the Walmart guild.
The other one will help you find where your lost grocery cart is.
One is a vendor, who likes you a lot and you roleplayed you have various love affairs with her outside of Walmart. OH and you Speechcraft minigamed her (she likes jokes and hates threats, the rest you don't care for) so she gives you discounts for weapons you will never buy.
One will be a beggar who will ask you for money in exchange for the location of the Black Seagull, master Herbalist.
One will ask you to aid him and his two other named, but not important, combat friends who will probably die in the assault because the AI is [censored] and there are no good target healing abilities. And once you are done with the quest and they are still alive they will just stand around with great depth.
One will be programmed to drink wine at exactly 5:57 am and who's rumors will consist of hearing another rumor about the slaughter at the church of Dibella.
And one is named Martin who will ask you to recruit 2 other named, but not important characters in the unepic fight against the Plus Sized Oblivion Gate.
The last one is a Walmartian guard who stops you for killing the rest of these NPC's for not having a backstory.
One will give an exceptionally destructive spell that you can't use because you got the quest at too high of a level and Magicka doesn't scale. She'll later tell you that she is the 16th and you should learn how to count.
THERE'S YOUR GAME.
Elder Scrolls VI: Walmart