.338 best all around
I think the .338 Win Mag is the single best round for an all round rifle, in North America.
Excellant ammo availability.
Reasonably flat shooting with good terminal performance at long range.
Big enough for animals that need to be anchored by one shot. Example of this are Moose on the edge of rivers, Elk on ridges above steep, brushy canyons, and Sheep and Goats on mountainous precipices.
Big enough for Brown Bear.
Perfectly acceptable for deer.