“the core bit would not to be to really have any stories, but just lots of non-player characters with lots of stats and interests.”
You’re right Chris, that idea is very Sims-like. I think the problem with it is that there’s no actual storytelling. Yes, with a good system you’re going to get very creative character interaction and development, but it has no story beyond that character interaction. With enough NPC programming and user commitment, can that character interaction develop into stories? I would argue against your basic premise (that this would work) and say instead that planned stories, of the epic variety, are neccessary to adventure games, and without those you do not have an adventure game.
“though I suspect there are still other versions without having to break down and put in RPG stuff.”
Interestingly enough, many RPG-like story elements are in adventure games – dungeons, monsters, heroes, magic, etc. It’s not a mistake to include some RPG elements in an adventure game – take Sierra’s Quest for Glory series. It stands as one of Sierra’s original and top five adventure series (King’s Quest, Space Quest, Leisure Suit Larry, Police Quest, Quest for Glory). One of the most unique Sierra games (Dynamix, actually) is Betrayal at Krondor. Sure, it was more RPG-oriented, but the story really shone through and it was released at a time (1993?) when the technology hadn’t exploded to the point that the interest was just in making great battle scenes or special effects. I’m not sure what my point with that was… just that in terms of playability, I’m not sure you’re going to get enough people to want to play your game idea. I’d rather play Sims than play a game with nothing else except for character interaction. Betrayal was a game that appealed to gamers across genres.