IMO, "Better" is in the eye of the holder.
(the camera holder 😀 ).
Only 'sort of'. Sharpness, vignetting, coma, astigmatism, contrast, distortion... It's not hard to agree about what is
technically better. What is
artistically better is a very different question.
If someone asks for advice on 'a good lens' it's quite difficult to give advice other than on a technical basis. If someone asks for advice on a good 9cm lens, I can point out that a Thambar at f/6.3 to f/9, for certain kinds of portraits and still lifes and landscapes,
in my experience, is stunning. I can also point out that it's heavy, slow focusing, far too soft at full aperture for most people's tastes (including mine), and ridiculously expensive.
As peterm1 points out, technically, many modern lenses are pretty incredible --- and very versatile and flexible. Given the choice of (for example) of various 9cm lenses, an Elmar, a Thambar, a first-generation pre-aspheric Summicron and second-generation pre-aspheric Summicron, the last is incomparably the most versatile lens that will suit the biggest number of photographers. This does not negate the undeniable truth that some people will prefer one of the others -- or indeed a Canon, Zeiss, Apo-Lanthar or whatever. But if someone is asking, "What's a good lens", do they REALLY want to hear (as if it were a conclusive argument) that so-and-so was the best available in the 1940s and that nobody complained 65 years ago?
Cheers,
R.