What is the best long term investment in stock market?

"Best" depends a lot on your goals. For me personally, I think a mutual fund or exchange-traded fund (ETF) that invests in small-company stocks, particularly small-company value stocks, might be the best. It's diversified (because it owns many different stocks), so if one stock goes bankrupt, I don't lose all my money, but it also is historically the highest returning asset class.

Take a look at this 7-year graph to see how the IWN (Small company value) ETF has outperformed the IWM (Small company) which has outperformed the Dow (^DJI), S&P 500, (^GPSC) and NASDAQ (^IXIC). http://finance.yahoo.com/q/ta?s=IWM&t=my...

Longer-term results show a similar pattern.

best is way too subjective of a term, but here goes:

I'd invest in a diversified stock mutual fund.

Nobody knows. What is best for one, is bad for another. 100 years ago, most people thought the new noisy, dirty allways broken down "automobile" would never amount to much and buggy whips would be the "best" investment. A few years later, Henry Ford's Model T proved them wrong. 25 years ago, people thought, why wait a week to see pictures when a "Polaroid" is ready in 60 seconds. Where are they now? Maybe something used by most people in the world, used everyday, used up quickly and bought again is todays "best" investment. Soap has been around for hundreds of years, will Proctor & Gamble, Colgate Palmolive, Dial, etc. still be making it 100 years from now? Or next year will someone invent a "cleaning ray" where you step into a "shower" fully clothed, turn on the "lignt cleaning ray" for 30 seconds and both your clothes and you are fully clean? Whatever you choose, keep a watch on it. The "best" of today can be the buggy whip of tomorrow. If you don't have the time to keep close watch on your investment, then I agree with the first responder, a well diversified mutual fund, with a hand in everything maybe best (a combination of safety and past returns).

IVV, SPY