That Cardus quote is pretty silly. Ultimately cricket is about one team scoring more runs than the other. Batsmen who help their team do that much better than others are considered great. And if I am not mistaken 39 was an excellent average in Trumper's day so there is ample statistical reason to consider him a great. However if he averaged 25 while batting just as beautifully presumably even Cardus wouldn't call him that. In the end it boils down to the numbers.