There are other ways! We actually know little of a person from his or her achievements. These are only sporadic reports, sporadic in that they are few and spotty. The real work, struggle, abilities available to acheive, and all the obstacles and turns in the way to each achievement are only partially known. This is why I suspect Einstein, a man famous for amazing achievements, regarded, perhaps, Emmy Noether, a woman who remains almost forgotten today, as his greater in achievements. The truely gifted -- which includes those who work very hard for those "gifts" -- can generally recogonize a fellow gifted person in their field after a brief close interaction.