I feel like everyone else here, my caliber choice is the best! As stated already this is a discussion of long range shooting. So that in mind, no situation is going to be ideal. There will be days when a 200 yard shot at a bull elk is almost impossible, and with the same rifle, days later, a 500 yard shot at a coyote is an easy "bang flop". I will say that many times I have witnessed people who simply can not accurately dispatch animals of any size, at any range, with their rifle of choice, and 90% of the time it has something to do with recoil.
All of this has been previously stated, but here is my 2 cents. Bullet selection is the key word here, an ideal bullet at 800 yards will very often act like a varmit bullet at 27 feet. From my experience, solid copper bullets are not always the best bullet choice at true long range. I will say in a situation I have found myself in this season, my preferred rifle, a 308 win,which usually shoots 1/2 moa 168 barnes groups, looked more like a 1 1/2 inch shot gun pattern. This my friends is bad timing for barrel work. This is my choice I typically use with amazing results on elk out to 500 yards. I use 200AB in my 300RUM with devastating results, for that 500-800 range.
The 165 Accubond at 2900fps shoot sub moa out of my 308Win, but my finding this year were at 100 yards, a head shot obviously was deadly, but the closer then usual range chest shot, the Accubond was less then stellar. The first shot had the animal bleeding from its nose(dead on its feet) The wind was blowing snow so hard, that after the first shot, a severe series of gusts, put me in a situation where I did not see the animal for about 1 minute, which seemed like forever. I hate to let animals stand there and die so I took another high shoulder. The first bullet would have effectively killed the elk, but did not make it through the other side of the chest which is what collapses lungs effectively.
For kicks I will say that a friend of mine chose to use her 375H&H on elk this year, a rifle bought for an up coming Alaska and Africa trip, and worthy experiment . It worked great on her cow at 100 yards. Hunting a few weeks later, was very discouraging when she could not hit a bull at 455 yards and her boyfriend wacked it instead. The next day she smartened up, and used the boyfriend's 300 weatherby to kill a 350 bull, and now owns this rifle also.
As we all know long range for one person, is not long range for another. Either way, hit or miss, you have to travel to the target's location. So if you choose a lighter side weapon that suits you, then you get closer while the animal is still alive. If you choose the "man Cannon", or your "lady Long Ranger" then you close the distance in celebration.
A wise man (we all have one) once told me to burn up lots of powder, they make it new every day. That is how you figure out which rifle is the best.