I have some lenses that I would term good or favorite because they seem to me to be lucky. That is, regardless of their technical merits or not, I always seem to get great pictures with them when I use them.
Now I would be the first to admit this is not scientific and indeed not necessarily that rational - but, in real world situations this feeling does result in me reaching for these lenses. And as photography to me is more about the pictures that I produce than anything else this is quite an important feature of what I would call a 'good' lens.
As an example, I have a m42 Schneider 35mm f2.8 curtagon that I can see is not technically the best lenses but does seem to get the pictures and have a higher hit rate than other lenses in that focal length.
A good lens to me is one that I can afford that takes good pictures. As of yet I have not found any that would qualify as a bad lens.
To me a 'Good Lens' is acceptably sharp wide open, with decent contrast and colour. It's got low distortion, preferably barrel distortion rather than moustache or pincushion. The out of focus rendering is smooth and round. It's neither massive nor tiny, has a reasonably damped focus ring, a smooth and positive aperture ring and doesn't tend to come apart when it spends a week at the bottom of a bag.
By those standards, most of my lenses are good and a couple are bad. The exception to the rule is the Sigma 24/2.8 Superwide II, which is good by optical standards, but a little recalcitrant from a handling perspective.
I've owned a few 'bad' lenses. Still have 2 (Kenlock 135/2.8 screwmount, Soligor 35/2.8 screwmount) as they aren't worth getting rid of, and the Kenlock actually produces decent images as long as I'm willing to scan them, add contrast and sharpen.
For me, a good lens is the one that can cope with the specific situation I am photographing and can extract as much detail as possible from the elements in the frame. Obviously this is limited by the format, type of camera and especially....money.
A good lens is one you don't notice in the photograph.
A good lens is like a good friend, you know it intimatly and exactly what to expect from it. It is the one lens you always want to use.
I have had this discussion repeatedly elsewhere where where would-be-experts tell people to buy L series lenses for their Canon cameras because they are the 'best'. When I enquire as to why they are best I get told things like 'they are tack sharp right up to the corners' (an actual response I got). My point was - if you look at your photographs and think they are not good enough because they are not 'tack sharp' in the corners, then you need a Canon L series lens. Personally, I have never thought that.
I don't worry about lenses too much - I am not overly bothered by technology at all - but I sell more pictures taken with a fifty-odd year old Tessar than I do taken with my expensive modern (not L series!) lenses.