It's funny, I feel the exact opposite. I feel the quests are much more compelling, the characters are much more interesting, and overall, this game has exceeded my expectations :celebration:
Yeah, same here (aside from some serious performance issues on the PC, but that's been solved now).
I feel like F3 basically put everything into the intro, and then it kind of dumped you into a world without much character afterwards. The intro sequences were so compelling that it kind of gave you the momentum you needed to get to each next major production element, leading up to the giant robot scene at the end. There was plenty of stuff to explore in between, but it was mostly inconsequential; you rarely engaged in interesting side-quests and generally just moved from one Oblivion-style "dungeon" to another collecting loot. That's not to say I didn't enjoy F3... it was great to be back in the Fallout universe, and the gameplay mechanics were all fairly fresh so it was certainly fun to play, but I always felt like I was not particularly involved in the events of the world so much as just wandering through killing things and collecting stuff.
Fallout:NV starts off really slowly and builds over time, very much like the original Fallouts. I don't want to turn this into a spoilers thread, but things get more interesting as you move on (the first two towns are basically part of an extra-long tutorial, IMO). As a big fan of F1/F2, playing NV feels like coming home. That said, you might still not like it if you felt F3 was really compelling from a plot/writing perspective. And of course the gameplay and graphics are certainly no longer new and impressive, so obviously that aspect of novelty isn't going to be there.
As far as complaints that the world feels kind of low-population, I think this is unfortunately just a concession made for consoles and lower end systems. It was exactly the same in F3, the population of the towns and such felt very limited, and I think it's mostly because there are only so many NPCs you can put on screen on weaker hardware without things bogging down on those systems.