I came across this excellent paper on excellence: http://www.simoleonsense.com/the-nature-of-excellence-the-importance-of-mastering-the-mundane-why-more-practice-wont-make-you-better/
I found it when I went to http://www.simoleonsense.com to check Paul Lountiz interview on scuttlebutt approach.
Do read the original paper at http://manzoid.com/static/mundanity_of_excellence.pdf
Worth a read by all.
After reading this we may now hesitate to say that some one is good investor. We should rather say some one is different kind (in some qualitative way) of investor. His theory of different worlds (rather than straight vertical ladder) in competitive swimming was very insightful. Also his advice that doing more of same will not make some one better.