New Vegas is TOTALLY the Fallout 2 to FO3's Fallout 1.
This is true on most levels, really. Both of them were created by a different team a comparitively short time afterwards, basically recycling many art assets and the engine wholesale, with a few mechanic and interface upgrades.
I mean, they were basically even made by the same TEAM. Obsidian is largely made up of the Fallout 2 guys. NV even had Marcus from Fo2 show up.
Not really apropos of anything, just interesting how history has repeated itself... though it is odd that Fallout 2 is considered a sequel even though it changes and updates less than New Vegas did from Fallout 3 (Companion wheel, Crafting, Reputation, Companion quests, multiple main plots, etc.) Why is that, do you think?