I don't think we can say that either is strictly "better" than the other. Here's my comparison:
Definitely takes the prize for pace and storytelling, a suspense filled drama that feels like death follows you around. Difficulty and gameplay were perfectly balanced against one another, with scarce resources and enemies everywhere, and finally great characters that grip you (NV has that too). However it is a little restrictive with choices, and the stock ending does end abruptly.
Better gameplay than 3, with its fixed gun mechanics, a dark comedy jam with funny characters, familiar faces, and a much better environment than 3 (in my opinion I prefer the Mojave, but I'm a West Coast guy). Great new faction system, with questlines and choice for each of them. It only suffers from being a little too easy and atmosphere is a little lacking.
Both do exactly what they were designed to do perfectly, and it depends on either the personal preference or mood of the player to decide which they prefer. I love both equally, but if a choice would have to be made, I would take FNV, only due to the fact I love the weapon mechanics.
I may be mistaken, but I'm never wrong - Ser Charles Barkley