There are several great cartridges, but my book the 308 Win. is about as good as it gets.
I will say, I have an elk hunt coming in the winter of 2014 ... and am antsy about this as my "elk" rifle. I have both a 300 Win. Mag. and 338 Win. Mag. that I can shoot well and have 100% confidence in. But I have killed so much game with my 308 Win., it is going to be tough to leave it behind !!!