Charlseton Cave, Bloodborne Cave, Black Rock Cave, Great Khan Supply Cave, Cannibal Johnson's Cave, Broc Flower Cave......I could keep going but you've already been pwned.
Some of those are pretty poor examples of exploration and virtually all of them are poor examples of
meaningful exploration. There is really nothing in Cannibal Johnson's Cave and only some goodies in the great Khan supply cave. As for the rest, any "exploration" done in them is basically just shooting stuff up. Fallout 3, while it certainly had its "shoot em up places" did have many many places that had backstories and areas where I could feel emotionally attached to the world around me based on what I had read/seen. New Vegas accomplished something similar with its storyline, but not with its "dungeons" (in my opinion). The H n' H Tool factory is the one place that I can think of which gave me the same "Fallout 3 exploration" feel and is a good example of a "meaningful dungeon".
Don't get me wrong, I'm not saying New Vegas is a bad game (hell its an amazing game) but its gameplay takes a different approach than Fallout 3's (meaning through storyline and not the world).