You can make pretty much anything look like a good or bad investment if you pick your start and endpoints carefully.
I think the most interesting, non-arbitrary comparison would be an investment starting in 1971, because this whole discussion is really about a fiat currency system versus gold, and how people value gold relative to such a system. 1971 is when the U.S. went completely off of Gold to a fiat system.
At the end of 1971, a few years after Gold started trading on open markets, the price was $41.25 an ounce [1]. Today, it is $1,100 an ounce [2]. That is a 26 fold increase.
At the end of 1971, the DJIA was $900 a share [3]. Today, it is $10,000 a share [3]. That is an 11 fold increase.
Gold outperformed our current dollar system, since its inception, by more than two fold.
That's not to mention the fact that you didn't have to do anything with Gold -- you just held it. With our dollar system, you'd be a fool to just hold the dollars themselves (because of inflation), so you are forced to speculate in the stock market or other risky vehicles.
[1]: http://www.measuringworth.org/datasets/gold/ [2]: http://www.cmegroup.com/trading/metals/precious/gold.html [3]: http://www.google.com/finance?client=ob&q=INDEXDJX:DJI