As far as story structure goes, there is a lot of similarity between the two games. Both games start you with a MacGuffin to chase (Benny and the chip in New Vegas, Kellogg and Shaun in F4) in order to introduce you to the world and get you involved in its story. Then after you find the MacGuffin the situation in both games opens up and you find yourself being courted by competing factions and in a position to choose sides and determine the fate of the wasteland.
As to the protagonists backstory, there isn't that much of it. I knew my character was married, had a child and had served in the military during the war (when there was probably a draft so even his having been military tells you little about him). That's not a whole lot of definition. It doesn't even define his occupation, as we don't know what he did in the military. Was he a soldier? A pilot? A surgeon in a M.A.S.H. unit? A chaplain? A records clerk? Work in the motorpool? The cook? Really, except for providing him a link to the world (son) to get him involved in the story, there isn't much definition and he's not prohibitively defined.