In my view, such a comparison between stocks and gold (which is paper gold btw. in this case) has a number catches. Firstly, the stock market is in total bubble territory and the prices for most stocks are purely speculative and have no relation to the real value of the companies. Its only because of the QE and 0% interest policy of the central banks that stocks have reached todays highs. And this situation can quickly change. The inflated currency supply will sooner or later destroy the purchasing power of the fiat currencies. That of course also reflects on the objective value of stocks, since they are representing those fiat currencies.
Secondly, gold and silver (real physical) investments are not supposed to make profits. Their task is to preserve the purchasing power of a investment. That has worked pretty good so far in the past, and it probably will do so in the future too. As you said, their amount is finite and cannot be artificially increased, at least for the forseeable future.
Crypto currencies suffer from a number of flaws so far. The biggest is, that basically everybody can create new ones any time. Really they are also fiat currencies, that only have value as long as people believe they have value. Just like our regular currencies, only without the government backing.