Disagree, obviously there's less in 3's wasteland, because it's simply a flat space, but the DC ruin overshadows all of the walls in Vegas. Besides that, NV's walls are pretty much superfluous, the black mountain wall has holes in it that you can pass through, making it an annoyance more than a barrier, same with all of the others. Fallout 3's walls are there because there is nothing beyond them, that zone is an entirely different cell that only spawns after you go through some shitty metro system.
Nearly every area has something unique or useful in it. Many places have background stories. Some you can gather from computers, others just by looking around. Most of it doesn't stand out, nor should it. The lack of compelling characters to run into does dampen it somewhat but I generally prefer my post-apocalyptic games people free so it's not really an issue for me.
unique as in mostly useless named items with the same mesh/texture as the common, with hardly anything special going on. Tons of generic skill books that are so plentiful that finding them is like finding a stimpak. That's not a big problem if you like that barren grimdark feel, but the problem isn't the population density, but instead that there aren't compelling characters even when an area isn't "people free".
Only partially true. Some stuff is scaled, some isn't. You can run into yao guai and deathclaws at level 1 depending on where you go.
True, I'll give you that, but to compare, Fallout 1 has about twice(Or at least around twice.) the amount of dangerous zones, despite only having a handful of locations, whereas 3 has literally 3 locations like that, out of over 100 locations with level scaled random crap.
I couldn't stand the F2 tutorial so I never bothered with it but Fallout 1 didn't have much to explore at all. It was all one big, mostly empty map. It could have used a few dungeons that have fuck all to do with the main plot.
This is a matter of taste, I prefer exploring to find interesting locations instead of exploring to find level scaled generic dungeons with randomly generated, level scaled loot. plot related is no issue to me, I find it increases the quality of exploration that I can accidentally find Lou's camp in the first few minutes, more than hurts it. Fallout 3 did a lite version of that, wherein you can find your dad at different stages of inane crap, but for the most part it's no where near as substantial.
I'd also recommend you try FO2, I find it better for exploration as it is larger and more populated, although many locations can help you on your main quest, they aren't all tied directly into it. As well, since this is Fallout and not some generic post apocalyptic setting, there are compelling characters and interesting companions to find. Although it lacks in the kind of generic settlement you're looking for, I think it's just as satisfying, the way they did the encounters was also good, the things you encountered were dependant on zone, you could definitely encounter hordes of deathclaws and other very dangerous things depending on the direction you took.
But now that you've detailed your opinions I don't necessarily disagree with you, when it comes to finding generic with level scaled knick knacks FO3 stands supreme. Although NV has an equal amount of those locations, it has far too many compelling characters and interesting locations to be able to stand up to the former.
#1 Unless we count OWB, which crushes 3 in it's own "brand" of exploration.