The answer completely lies in your choice in selecting investments and the time you put into research.  The most common investment for those not in the business of investing is residential real estate due to the limited time involvement required and the safety of rental revenue.  There is limited data on what returns the rental properties make but we can assume it would depend on rent rate growth over inflation.  These returns have varied significantly over 10-year periods but have averaged about 1.25% over inflation since 1980.  The actual returns would depend largely on the purchase price but I would assume these market returns would be less than the S&P 500.   

The best investment you can make for yourself is investing in something that uses your trade skills or you have in-depth knowledge.  For example, if you have a pharmaceutical background and enjoy reading about medicine research you can specialize in investing in the biotech industry pharmaceutical companies.  If you have other hobbies or interests in your free time then investing should be left to index funds or invest with others that do this work.