I think the 0.4ohm standard that
@hakuzen set is fair, anything above that is quite poor, though there are some weird exceptions, like the cardas clear light sounding pretty great despite being close to 1ohm. The neotech non alloy upocc stuff seems to all hit below 0.2ohms, so I'd say that's probably what qualifies as very good.
On a side note the faaeal 5n litz is truly excellent, it's been the top of my list for buget cables for awhile now but didn't expect it to measure that well as well. It's a sub $20 cable that honestly gets you pretty close in terms of technical performance, like 80-90% of the way, of all the top coppers I've heard from the likes of toxic, dhc, plussound, effect, eletech etc. and in fact quite a bit better than some of the $100-250 from some other cable companies. I've told some others about it but they've all brushed it off due to the price, but the technical performance is remarkable even without looking at the price it's easily at least upper second tier sound quality wise. Fantastic value and highly recommended for anyone looking for an good copper cable.