I think there are definitive answer
s to the OPs question. 
But those answers are necessarily different for each photographer.
Which means, I think, that there is no one "best" 50mm lens but there is one "best for me" 50mm lens--or, more likely, there is one "best for me for this purpose for this time" 50mm lens.
And I can't tell you
 what the best lens is. At best, I can tell you 
why I prefer what I have chosen in such a way that you can decide if my choice 
might be worth trying to see if it works for you.
	
	
		
		
			Perhaps to phrase it another way: assuming that a lens meets minimal technical criteria, then the results it produces are simply a matter of taste. That is why I said that it would be good to get a relatively neutral party to judge the prints. It's no good having a lens which has the best ever pq² rating (I just made that up) if you don't actually like the pictures you can produce with it.
		
		
	 
Sorry, I disagree with this. I think it would be good for 
you to judge the prints. Exactly 
because it is a matter of taste. And your taste will be different than mine as mine is different than anyone else's. 
A more specific example: I own, like, and use primarily FSU lenses. Most of mine were made in the 1950s. 
For me, they 
are the best because they meet 
my criteria. 
Certainly lens designs and technology have advanced since then so my choice is not based on "technical criteria" alone--or even in major part--but is based on my wholly subjective criteria.
What I can and will suggest to you is that you do look at the kinds of comparisons you are interested in but not to bother with other peoples' conclusions. When you see that a particular lens captures things in a way that you like regardless of it's presumed technical qualities, then that may be a lens you should try to see if it really does meet your own subjective criteria.
Rob