Well, I have been through a number of guns in my time buying and selling. A few over rated in my mind are:
7mm rem mag. I have witnessed a number of deer hit good make it a long way with very little blood.
303 British. Yes I said it, it delivers decent power but is made in heavy old clunky guns that can have headspace issues. For the average person they can be troublesome.
223 rem. Had one that was incredibly accurate, cheap components, but never really was satisfied with it.
I have a Creedmoor on its way back from the gun dr. I am not sold on that chambering, however I have not witnessed it’s on game performance yet.