Yeah I'm jumping on late to this but here it is anyway.
I think this example is problematic. Are you saying that the Ultramarines are the greatest because the politicians say so? The high lords of terra (just like everyone else) have their own agendas. Their praise of the Ultramarines only implies that the UM's serve their purpose the best. Also, saying that the UM's are the greatest in the eyes of the imperium is an incorrect statement. There are several accounts throughout 40k lore that single out different societies revering one primarch/chapter over all others.
Looking at my avatar you can see plainly which legion I prefer. Do I think they are the greatest? Yes. Do I care if you agree? No. The Space Wolves display the things that I believe reflect the best things about humanity and I am more than willing to accept that someone else can see the same things in the Ultramarines, the Blood Angels, the Imperial Fists or any other legion.
