I've only played the game. I haven't read the manga.
Q: 〇〇漫画を読んだ?
have you read 〇〇漫画?
A: その漫画はゲームしかやってない
no I've only played the game. I haven't read the manga
が自然な返事になりますね。
I've only played the gameだけでも通じると思います!I've only watched the movie (映画の場合)、I've only played the game (ゲーム)などの場合でよく使う表現です。
ご参考になれば幸いです。