The perfect cartridge is the most efficient ( least amount of powder, noise and recoil),that will ethically kill the animal you are hunting at the range you are taking your shot.
If you want one cartridge for all game it will be a poor compromise.
For large(1000lbs) non dangerous game. Depending on your tolerance to recoil:
Less than 200 yds. I like 9.3x57, .35 Whelen, 30-06,(220gr).
Over 200 yds. .338 Win Mag, .300 Win Mag, 8x68S.
There are several "perfect cartridges" for every animal at every distance and condition possible. What your local gun shop sells the most may be the best for you.

My favorites are the .22LR, .223Rem. .270 Win, .30-06, 8x57, 9.3x57, 9.3x62, .340 WBY, .375 H&H, .458 Lott but I have many others as well. The caliber is often limited to the rifle that chambers it. The finest Mauser action guns have older well proven calibers. If you want a Weatherby, Ultramag , Lapua Lazzeroni, Ruger or Blaser cartridge you are limited to certain brands.