To me, there is no best shotgun guage.
I agree there is no best gauge, but there are preferences. The question asked was not best, but "favorite"
Nearly every great hunting memory I have is with a 16.
My favorite remains 16 for everything, though I do own a 24, a 12, and two 20's, the core of my collection is comprised of six 16ga guns. I don't count i herited family guns.
Hunting gun preferences are in my experience linked to particular guns more than gauges, though gauges play a part. Sometimes by luck or chance you get the right gun that fits and hits and the habit and like grows.
The two best guns for me are similarly balanced, weigh within an ounce, and barrels are within an inch. Both are 16ga. Out of habit I have stayed with 16 from when I was a kid hunting my Father's German guild gun, though my Fox Sterlingworth, my Browning 16 O/U, to my Louis Christophe and lastly a beat-up Purdey project gun.
There are one or two purchases ileft in my future and they will more than likely be 16's.
I make no claim that 16 is uniquely superior, in fact while ballisticly sufficent for the uplands, and for me just right at 6lbs and a few ounces plus or minus, feeding the beast is a pain. If you shoot 16 alot, you will probably become a reloader.
Through habit, the feel of a well balanced 6ib gun feels just right to me. If I had brought a good english 12 SLE in 1985 whem I had the chance I might be favoring a 12 gauge 6 1/2 pound gun.
Everyone has their own predilections and preferences, mine is 16.
Most of my "best" guns are 16's. For more than 30 years I have loaded and collected 16ga tools, components, and ammo. At this point I am over committed and will not change.