Just what is a good lubricant? I once did a science project with my son where we tested a number of liquids on skateboard wheel bearings. Each liquid was applied in turn to a clean, dry set of bearings in a wheel. The wheel was mounted, run up to a uniform speed and allowed to spin until it stopped.
What gave the longest run? Brake parts cleaner. Next was plain water. WD40 was right up there. Dupont teflon lube was pretty good. None of the oils, all supposedly better lubricants, fared so well.
I know from my own experience with motorcycles, and from my reading on the subject, for a chain that is run offroad, in a dirty environment, that no chain treatment regimen has been shown to give longer chain life than regular dousings with WD40, except for a continuous supply of oil applied with a chain oiler that runs constantly. Proprietary chain "lubes": all worthless. None of them has ever been shown to have any effect on chain life. 90w gear oil, a great lubricant when applied continuously, has been known to shorten chain life in the conditions I describe.
That does not necessarily mean that WD40 is the best chain lubricant, or even a good lubricant. It all depends what you are testing for.