I'm not.
I love FO4.
I've spent more time with it than TW3 and probably (just) prefer the game to that.
But I recognise that FO4 sits on slightly older technology, and doesn't quite meet the depth of story-telling that TW3 pulls off.
In short it is not quite the 'new shiny' that TW3 is.
FO4 currently has more GOTYs than MGS, sitting as it does in second place, which is fair and still pretty damn good.
TW3 raised the bar for storytelling which is good news (and an incentive) for all AAA games going forward.