Do you know any game which actually uses cryptocurrency? I saw a lot of coins which promise this, but usually It ends up in being scams.
Games are for fun, but It would be more satisfying to have a valuable currency for games.
The most famous project which is a cryptocurrency and is also very closely related to games in Electroneum. Electroneum is a coin one can mine of one's mobile phone by playing games. When it started as an ICO people were really excited, but after it was released there were some issues with the game and people became less interested. However, I believe it is still possible to play and mine.
Another thing that comes to my mind is tons of casinos which accept payment in top coin or are even built on ethereum platform (they use smart contracts to prove they are scam-free), like Vdice.