Been pondering a bit: What makes an investor great?
The returns? The longevity in the trade?
I apologize in advance for the long answer but it's a very nuanced topic. I'm going to approach this question from an institutional investing perspective.
I've previously worked at a fund of funds (a fund that invests in hedge funds) and one of the hardest problems was separating skill from luck. It's not an easy task for hedge funds and it's even harder to identify skilled individual investors due to the larger size of that cohort. Essentially the larger the cohort the higher the probability that someone will be successful by pure chance
I think this could use some more rigorous study from an academic perspective. For instance, using @investmenttalk metric of 10 years, what's the probability that the investor continues to make money over the next 5 years. In a naive implementation you could assume that the people that lose money during that time relied on luck and the one's that made money had skill. But a more realistic answer is more complicated, hence the need for more study.
But if anyone manages to figure this out they should create their own Fund of Funds or become an asset allocator for an endowment!