Let me first say that Fallout New Vegas is my favorite game of all time. That said, I’m not sure I recommend it for the OP. Here’s why.
Fallout 1 was an isometric RPG.
Fallout 2 was an isometric RPG.
Fallout 3 was a 3-D RPG.
Fallout New Vegas was a 3-D RPG.
Fallout 4 was a first person shooter.
One of these things is not like the others. 
If you are an RPG fan, Fallout and the Elder Scrolls were the two best things out there for years. Bethesda (with some help by Obsidian for FNV) was the undisputed king of the RPG.
But there is a valid criticism of RPGs in general. A really good RPG has a lot of lore and depth, and you really have to think to get immersed in all of it. For a casual gamer who doesn’t want to spend that much time and effort, true RPGs can be confusing and difficult. But you can’t have it both ways. Either the game is designed for RPG fans who love depth and lore and want to be immersed in a deep and complex setting, or the game is designed for casual games who can play through without a lot of thought.
In Fallout New Vegas, what you do at every step matters. There is a lot of depth and importance in many of the conversations. Say the wrong thing to someone, and you can lock off entire quests. To a casual gamer, all of these conversation options are annoying and cumbersome. To an RPG player, they are the meat of the game and are essential to an in-depth RPG experience. Fallout 4 by comparison is much different. Every conversation ends in the same place. There’s no branching. This is what you expect of a shooter, where the conversations just move the plot along so that you can get to the next exciting combat.
This is why Fallout 4 is hated so much by Fallout fans. The Fallout franchise up to that point had been one of the best in-depth series RPG games around. And then Fallout 4 came along and it wasn’t really an RPG. You only make one choice in all of Fallout 4, which faction you want to win. The rest is completely linear, and all other conversation options don’t matter.
Fallout 3 has one ending. Fallout 4 has four endings. Fallout New Vegas has different endings for each faction. There are four main factions, so four main endings, but then each lesser faction has multiple different endings, so the total number of possible endings is rather huge. Again, great for an RPG, but way too complex for a casual game.
The OP likes the first person shooter and the world building. By comparison, Fallout New Vegas has a clunky combat system that is best described as adequate for an RPG but kinda lacking for a shooter. Fallout New Vegas also has no world building, though there are mods for that (in fact, Fallout 4 got the idea for world building from one of FNV’s more popular mods). The OP also likes scavenging and crafting, which exists in FNV but is much more limited and doesn’t tie into the world building system (because FNV doesn’t have a world building system).
Feral ghouls are a bit terrifying in FO4. They are much more mundane in FNV, to the point where if you started with FO4, you are going to be downright disappointed by FNV’s ghouls.
Power armor was greatly improved for FO4. You are going to be sorely disappointed in FNV’s version of power armor as well. FNV’s power armor feels more like you are just strapping on an outfit. It doesn’t have the feel of something massive and mechanical like FO4’s version. If you like chunking around in heavy power armor while blasting away at nasty wasteland critters, you are going to be disappointed in FNV.
As far as the dark humor goes, that is better in the older games, especially in Fallout 1 and 2. FO4’s quirkiness and dark humor is significantly watered down compared to the older games.
FO3’s storyline is very linear, but it is interesting and well done.
FNV has the best storyline, just because you have so many options while playing through it. One valid criticism of FNV’s storyline is that unlike every other game in the series, you don’t start out in a vault and you’re not a vault dweller.
FO4’s storyline is ham-fisted and horrible and has huge gaping plot holes everywhere. So yes, compared to FO4, FO3’s storyline is definitely better.
The OP doesn’t mention mods. If you get into modding your game, FO3, FNV, and FO4 are all heavily moddable. However, mod support in FO3 and FNV is clunky and fiddly. Installing mods on FO4 is much easier.
As far as the Elder Scrolls series goes, that series did not have the huge change in direction that Fallout experienced between FNV and FO4, but the Elder Scrolls series has slowly been moving away from the in-depth RPG to a more casual gaming type of style. The quests in Skyrim are simpler, the puzzles are basically kindergarten-level, and the side quests are short. If you do the College of Winterhold quests for example, it’s basically you do a couple of minor things and POOF! You’re now the Arch-Mage, in charge of the entire college.
I think the OP would like Skyrim, though. There’s no world building, and crafting is limited, but you can stomp around through combat after combat, then take a break and get involved in some short side quests or just go roaming around looking for bad guys and bad creatures to wipe out. The storyline is a lot better than FO4’s storyline, though Skyrim’s storyline is more than a bit formulaic.