If we are to believe some of the literature on the Internet, there once existed a golden age of manual lenses that has been lost and covered up by manufacturers of digital cameras wanting to push their modern-day inferior auto-focus lenses on the unsuspecting public. Some people read about this and decide to redress the balance by building up a collection of these older manual focus "better lenses". But this is all hype and nonsense. A modern auto-focus lens (unless a third-party lens) designed for digital format (i.e. not a old manual focus lens design that has been converted to auto-focus) will be better than any of these manual focus lenses, 99% of the time. The only exception being that some of these old lenses have a very good bokeh. Bokeh is to do with lens construction - it isn't a technique to be learned. If bokeh is very important to you then by all means build up a collection of manual lenses with good bokeh, but don't waste your money building up a collection of manual lenses trying to get better lens resolution, because it just won't work.
Here is the first thing to consider about older manual focus lenses. That is that their full aperture was not expected to be used, except in rare situations where small depth of field was essential and it did not matter about resolution much outside the centre of the image. That largest aperture was there to help you focus more easily in poor light. It made the image in your manual split-screen microprism finder easier to see and hence easier to focus more accurately. If you can't focus accurately then you have a blurred image and your image is worthless. You paid big money for a wider aperture lens to let more light through for focusing purposes. The lens itself was expected to perform well when stopped down by two stops such that an f/1.4 lens would need to be stopped down through f/2.0 to f/2.8 before it would perform well. Auto-focus lenses do not need this wider aperture to help them focus. They focus better than your eye can (assuming you are using original manufacturers' lenses and not third party lenses and you are not using Sony cameras where you have to adjust the autofocusing yourself to get it to work accurately). So these more modern lenses are designed and constructed around the superior ability to focus automatically. That is, if the lens has been redesigned for the digital format. But not all lenses have been updated for the digital format. For some of these lenses we have the identical manual lens as before but with auto-focus added.
If you check out the older Canon and Nikon lenses on this list then you will find that they likely have poor corner resolution at widest aperture. These are the old manual focus lenses that have had an auto-focus make-over. These will all be replaced with more modern designs that give you better corner resolution at widest aperture. And this is the main reason why you should not be paying money for these old lenses. They never were much good at their two widest apertures and therefore they are not worth collecting.
I don't care - I still want to use manual lenses
I sometimes use manual lenses without much of a good reason. If I am taking photos of a historic town in Germany and want to give it a 1940's or 1950's look then I like to use lenses made in Germany (for the Bessamatic) if I am not too bothered about resolution. And this gives me the problem of focusing the lens. With manual cameras your viewfinder focusing screen had a split prism at the centre surrounded by microprisms and focusing could be done very accurately. With modern cameras you don't have such a focusing screen or if you get one then chances are it will not fit precisely in the film plane. Instead, you have a matte screen which is very hard to use for manual focusing because the image appears to be in focus when it isn't. Can