So which do you consider to be the best of the best?
What is the criteria ?
Unless we identify our subjective standards,
we can't KNOW what is GOOD,
let alone BEST.
No outside sources allowed,
let's think for ourselves.
For me, a 50mm is a portrait lens, used in low light, often under an open sky, on a Leica.
I need a clean, well balanced image, with good roundness ( a term we used to describe some of the qualities 'good bokeh' has recently come to represent ): sharp, but not spiky or wirey. I KNOW this quality is the result of less than 2006 optical perfecction, but then, it suits the pictures perfectly.
I love my 1950's Summicron because it still makes fine pictures on my Leica. I make use of it's slight wide open softness to take the 'edge' off portraits, yet it is still a clean image.
I like the 1950's 50/1.4 Nikkor on the Leica for it's clarity wide open... without paying for a new Summilux, which is a far better lens but more than I need for the purpose. It's a virtual replica of the '50s Sonnar (on the Contax left to me by my first teacher).
The Sonnar and the Summicron are complimentary, and are great lenses to have in the bag.