I learned to shoot with a pre-War 5 shot Browning in 16 gauge and used it for everything, quail, rabbits and ducks. It was not until I started shooting skeet that I turned my back on that gauge. Since then, ammunition has been harder and harder to find, and when I do find it, there is a distinct limitation in the choice of loads. For that reason, I have turned to the 3" Magnum 20 gauge for a lightweight hunting gun.

My Krieghoff "Teck" O/U double rifle in .458 WM was built on a 16 gauge frame, because Krieghoff didn't offer a 12 gauge version of the action at the time. They now do, and I have a .500 NE built on that frame.

I ordered shot barrels for my .458 DR, but chose 20 gauge Magnum over 16 gauge because of ammunition availability. It proved to be a real winner, whether on sand grouse, guinea fowl or ducks in Africa.
I'll believe the 16 gauge has made a comeback when I see an assortment of ammunition on the shelves.