Glad you said that Rook. I don't agree with your view on Fallout 3's writing but I will agree it is Linear which svcks for me because Fallout is meant to be an RPG and to me that means options, lots of options and Fallout 3 has very little in the way of options.
So many Fallout 3 fans will fight tooth and nail saying Fallout 3 isn't linear. I am glad you arn't one of them.
No ending does not always = non-linear.
Linear, not to be able to go in whatever direction that you may choose because the game does not allow it at that particular time in game-play.
Fallout 3 is certainly more open-play non-linear than New Vegas.
The main quest, by it's nature of giving an aim and direction to the game, has a degree of being linear, but even that linearity can be bypassed in the open-play of Fallout 3.
Linearity does however close off plot-holes where you could complete a section of the main quest "unintentionally" ... which I happened to do in FO3 by clearing out a location and finding well-hidden items of the main quest (linearity would have prevented that)... it was a nice surprise and a bonus to the game-play.
Moriarty, the initial quest contact actually said to me, “ you can try to find your father yourself and good luck in trying“ (words accurate enough).
Give me the more open-play of Fallout 3 any time.