Aye, 'tis most impressive.
The deviance between Toady and most other game developers is not a lack of scope, but rather losing interest/funding over time. The standard mainstream development cycle is too short to allow for a sophisticated game, and game engines (the bits that aren't coded from scratch) tend to focus on graphics and superficial kinetic physics over modelling other aspects of the world.
I would be very curious to see an initiative in games that focused on integrating a whole set of engines together, such as one for emotional modelling, one for structural physics, maybe one or several for magic (if it applies to the game), all tweaked into a cohesive whole. We might be able to get a variety of modular games of the same complexity as Dwarf Fortress (though likely nowhere nearly as coherently tied together without a lot of work.) There's a large hole between mods, even total conversions, and creating a new game. Maybe this will fill it. Anyway, 'tis offtopic.
As far as the current social framework of game development, a single person (and his brother helping) laboring for a long while is probably the best way to get something of this magnitude off the ground as long as he is truly commited to the project. I would have thought something of this scope impossible to make (keeping interest for that long is... difficult), but Toady's already gone a lot further than I would have predicted. Here's to hoping he'll keep at it - and with his track record, it looks like he will.