Which version of Fallout 3 did you play? What kind of character did you build?
I played it on a PS3, and I actually didn't quite finish it (I did finish it just to see the disappointing ending, but there are things I'd like to do first.. and at the end I ended up not playing the game again at all.)

I was a pretty evil female character.. blown up Megaton, enslaved a lot of people..

It's just disappointing how your actions and choices in the game didn't actually have anything to do with the endings, or how it could affect the choices you have at the end.