I kind of feel like you deserved to be disappointed if you actually expected 4 to be better than NV. NV was one of those once-in-a-generation gems, and Bethesda simply does not have the in-house talent to match it in the fields of writing, characterization, and interwoven / multi-path questlines. Beth did try their best, god bless 'em: the companions are modeled much more closely on NV's than FO3's, and the structure of FO4's main quest is lifted directly from NV, right down to the Yes Man > Minutemen 'we'll be here in case you fuck everything else up' afterthought of a faction option. And in this regard, structurally it blows FO3 out of the water at the very least - for all of FO4's main quest shortcomings, it beats the hell out of shoehorning me into being the Brotherhood of Bland's errand boy with the occasional opportunity to be a dick for no little to no reason.
Which is why I wasn't very let down with FO4, because it gave me what I wanted, but no more than I expected: an overall improvement over Fallout 3 (which is far from high praise in and of itself, but still...). It gave me settlement-building, something I've been craving in a Beth-formula game for a decade; it did a couple things best in the series (power armor, overworld density); it made several improvements over Fallout 3 (far better combat, better and more in-depth companions, better DLC, more logical worldbuilding, making the main quest plot intrinsic to the world), and took a few steps back (stats, skill checks in dialogue). So overall it was at the very least an improvement to the formula, which is far more preferable than an overall step back.
Simple questions deserve long-winded answers that no one will bother to read.
