The problem is you could have actually owned gold for 90 years. Average Joe could have bought gold and held it.
You could not have owned the Dow index for 90 years and then left that to your children or grandchildren.
Would you like to still be holding Polaroid or Kodak? Or perhaps just bought and held the classic Dow index perpetual GM? You would have gotten wiped out in the Dow shuffling. The Dow gets to drop something like GM at its convenience, but if you had bought its stocks in a basket format (not an ETF), you'd literally be holding worthless old GM shares, and a lot of other worthless shares that they don't currently count in today's Dow numbers.
The Dow calculation is a theoretical, not an actual. 90 years ago only a very savvy investor could have owned a basket of stocks to mirror and index exactly and constantly traded in and out of the market. In 1920, an exceedingly small % of people owned or had access to equity markets.
Buffet using even 1965 as the reference point is disingenuous because of those reasons. His scenario is not a normal one: he used his father's brokerage firm to commit his first market transactions back in his early days. How many Dow tracking ETFs existed in 1965? How many people owned stocks in 1965? Today you can open an account at Scottrade or wherever, and pay a mere $7 transaction fee to buy stocks.