Fallout 3 can be seen as a separate game with a similar world. IMHO.
Therefore, I don't think it's as big of a problem as fans of parts 1 and 2 say.
I played Oblivion a lot, and to be honest, Fallout 3 got boring for me pretty quickly because of their many similarities.
Bow down and hear our cry,
Our earthly rulers falter,
Our people drift and die,
The walls of gold entomb us,
The swords of scorn divide,
Take not thy thunder from us,
Take away our pride.
G.K. Chesterton: English Hymnal