There are a lot of .308 calibers out there that perform very well. 308 was created as a NATO round, thus most sniper rifles were chambered for that due to ammo availability along with it being a short action bolt rifle. Plus, .308 caliber ballistics are hard to beat.
There are many calibers out there that will out perform the 308 in accuracy and ballistics, but the short action had the appeal.
Some of the calibers that are just as accurate if not more, with much better ballistics: 300 Win mag, 308 Norma Mag. With these two you would just have to accept the magnum (Long) action along with a lot more recoil. But, then again, that's what muzzle brakes are for.