Chipotle Mexican Grill still offers a huge opportunity to investors.Over the long term, the stock market has been an incredible wealth-building machine for patient investors. For example, if you had invested $1,000 in the S&P 500 in 2006 and reinvested your dividends along the way, you'd have a stake worth about $6,000 today, an annualized return of 10.6%.That's a safe way to grow your money. But if you had invested in some individual stocks as well, you might have a lot more. That's the beauty of a diversi ...