No, gold reward coins on an app game could not be considered a form of cryptocurrency. From my point of view, there are two major differences. The first is the very technologies underpinning the two—cryptocurrencies, for example, are built atop blockchain and use strong cryptography for ensuring transactions security. Secondly, cryptocurrency prices are based on supply and demand, while in-game coins are sold at a fixed rate established by the company that developed the game itself. Rather, coins that you've mentioned are a form of virtual currency, and both virtual currency and cryptocurrency are forms of digital currency.
You can read an extended version of my answer to a related question here.
In short, what understood to be "cryptocurrency" is not really issued by anyone in particular, and arguably having an issuer, or any party that can unilaterally change the balances of any account, by definition excludes that currency from the "crypto" world.
Cryptocurrency is not just about being an electronic balance, it's about a balance that is safeguarded by protocol, which transparently and strictly governs how the currency is created and transferred. So Farmville money, or any money that can be created arbitrarily, by fiat, is arguably not crypto.