Are Fidelity 500 Index (FXAIX) Funds a good long-term investment?

Yes, Fidelity 500 Index fund is certainly a good place to invest, especially if you are looking for long-term profits. It has a very low expense ratio which is 0.015%, while it has a long-term 10-year average return of over 12%. However, Fidelity 500 Index fund might not be ideal for short-term investment.