I don't know whether having a massive 'open world' really matters, because you can't scale storytelling. The trick of all of these games is having a feel that a larger world exists, but at the same time leading you along a relatively narrow path, along a meaningful story.

Also true. But still, coming from that point of view, the illusion is easier to see through in FO1/2. E.g. the idea of walking through the wasteland vs just seeing a dot move over a map with some random encounters. Back then there weren't many games were you could really explore the world, so this illusion was quite good at giving you the feel of having a huge map with real events happening. It won't do that to a person who played Skyrim and GTAV.

On the one hand, seeing a dot travel across a map may make it feel like they aren't "really" moving.

On the other hand, taking several thousand squares miles of real-world space and stuffing it into about ten square miles can make it feel like the world is awfully claustrophobic. In the real world, it would be perfectly sensible for a slightly out-of-the-way vault or something to be entirely undiscovered for decades at a time, even with our current pre-catastrophe civilization. In the Fallout gamespace it seems faintly silly... "seriously dude, nobody ever took a five minute break from work to talk a walk and noticed this big, hulking thing?"

One game that actually did tackle this all the way was Arcanum.

For those who don't remember, what these guys did was make a seeded map generator that filled all those thousand square miles of real-world space between pre-designed locations with something appropriate. And you could literally leave a location, but just keep going without switching to the fast-travel "world map" - and if you went for long enough in the right direction, you'd get somewhere else. But, world size being to scale, you'd literally have to walk hours or days.

Consequently, when in fast travel, if you ran into some randomly generated monsters, the battle map would actually be that exact part of the generated world map. If you happened to run into something else again in the same spot (or close enough), you'd see the same map.

Of course, this made game design somewhat awkward, because if you knew the precise locations of things (they even used latitude/longtitude for map coordinates!), you could just go there right away - unless there was some choke point on the map that you couldn't avoid and that would require direct interaction (like, say, a lone bridge over a river with a bandit collecting toll from any passers-by). And the game was actually designed around that possibility!

The problem with all this is that it's a gargantuan effort to maintain a giant sandbox that most players will just ignore, or possibly never even discover.

I don't think that's true.

I can still get into a book even though I've seen movies. I think it takes a certain type of individual to get into the Fallout 1/2 style of interface, but the overall game still holds up. Older games require more imagination though.

I've gone back in and played the original wasteland recently, and it's cluunky - but I was still able to get into it and enjoy myself.

I think back in the day gamers had more imagination. It's possible that's because gaming required it, and that it took better graphics and interaction to get it so that the mass-market could adopt them. It's possible there's a branch of gamers who just won't be able to get into games like Fallout 1/2, but I hope it's fewer than you are describing.

Fallout 2 is still plenty big even by modern standards. Here's a quick question: how many city locations did it have? If you played a lot, but still can't answer right off the bat, it's probably "big enough".