You would think that about half the stocks in the S&P 500 do better than average in any given year. One would expect a balanced distribution between superior and inferior market performers.The reality is that the exact percentage moves up and down in real time. And generally speaking, only around 20% of the constituents of the S&P 500 outperform the market average. That's why finding a winner is such a big deal.According to MacroTrends, the five best stocks of the past decade are Nvidia (NVDA 0.39%), AMD (A ...