Thrasher
Wheeee!
If you're choosing to play NV before 3, then you must get the story DLC, in particular Dead Money, Old World Blues, Honest Hearts, and Lonesome Road. These DLC are the best parts of FO:NV. By best, I mean story, characters, and in some sense exploration and level design.
I myself would have a hard time picking between FO3 and FO:NV. Both are strong on their own merits, as discussed above, and both have some very annoying flaws. I have to say that FO:NV had a much stronger emotional impact on me than FO:3. Some of the stories and NPCs were extremely engaging. That's the sort of stuff I will remember from my playthrough. FO3, not so memorable for the characters and stories, but a little for the visuals.
I myself would have a hard time picking between FO3 and FO:NV. Both are strong on their own merits, as discussed above, and both have some very annoying flaws. I have to say that FO:NV had a much stronger emotional impact on me than FO:3. Some of the stories and NPCs were extremely engaging. That's the sort of stuff I will remember from my playthrough. FO3, not so memorable for the characters and stories, but a little for the visuals.