It definitely is. There are so many ICOs that offer coins through online gaming like casinos or what not. However, if you're pertaining to online video games, I think many developers have tried to implement some similar plans, but I am not sure if there are any successful or big ones that have actually worked out, since in this day and age, many people are not so into pay to play, most are more comfortable with free to play games. On the one hand, it can be introduced as a means to buy merchandise in-game, in that sense, the developers may introduce a game coin that people may buy with real money, which they can use as means to buy game items or to trade with other people for money which is the very essence and use of altcoins.