I couldn't stand going through those countless subways in fo3 fighting all those feral ghouls. In Nv in one of the vaults (sorry cant remember which one) you had to go through countless levels of fighting those green creatures or the quest where you had to help the ghouls fly off in the rocket but first you had to fight through all the invisible nightkin and feral ghouls. At least in NV you could skip some of this if you wanted but in fo3 you have to go through all those darned tunnels.
However I don't mind fighting somethings out in the wasteland like fire ants, brahmin and czadors*. I'd rather fight wild animals in the wasteland infected with radiation like wild bears.
I also wished there were more small raiding groups like the fiends that will always be hostile to you roaming the wasteland. I guess I just like fighting people and and smaller roaming animals rather than feral ghouls and big creatures/monsters.
Sorry for the typing errors I'm on my phone lol