I read an article this past week with the same question being asked, the general reply from the experts was most of the guns in the 30 cal category. Now, don't get me wrong, they mentioned alot of other calibers as well, but the 30 cal group was the favored.
I once again have to say it depends on the terrain and style of the hunter using that particular gun.
I hunt with a variety of different calibers, 7mm, .300 Savage, 444 Marlin, 12ga slug guns.
One thing I have observed and corrected with my set ups it the proper bullet weight for the job, when I first bought my 7mm, the only bullet weight available locally was 175 gr. I shot a few deer with that bullet weight but was not impressed with the results, I was getting hard hits, but straight pass throughs with small exit wounds. I finally was able to locate 150gr. and the performance was much better.
I started handloading and that is when the entire ball of wax changed dramatically. I was able to experiment with many different bullet styles and weights. I now have a great combo worked up for nearly all my rifles that dispatch a deer nicely.
So, my point being the caliber alone is not the only fact on what is best, better and so on.
FDXX75