"best"caliber for wilderness survival

In a survival scenario, obviously a rifle would be more useful than a handgun if only for the increased range and accuracy. As for caliber, the .22 mag is certainly a viable option IF you have a good supply of ammo on hand when you go into the situation. The .22 mag is not something you're likely to find lying around in the ruins of civilization. The .22 LR is everywhere, and much more likely to turn up among the ruins if you dig long enough.

Picking up ammo that someone else no longer needs may lead to other choices. An AR15 or M16 could be very handy, again considering the likely availability of ammo. It's almost as plentiful as .22 LR.

So it may all boil down to what you have on hand or can find in short order in your situation.

Good points! I was thinking in terms of the scenario of the TV show. Out there by yourself with your boots being the only transportation.
In a post apocalyptic scenario, I'd easily see 5.56/762x39/762x51 to be the choices. Whatever is common with the military in your AO at the time.