We need examples because there are 2 reasons I can think of for including furigana. 1 that the hiragana part is the pronunciation of another word, added only for double meaning, like some songs write 時間 but sing it as とき even though its pronunciation can only be じかん, and 2, because it's a rare word or a name. Personally, I've never encountered a game that includes furigana for words, I think doing it only for names is more reasonable. You're better off giving us an example. RPG games, for example, don't tend to include furigana because the player is expected to know many of the literary, archaic or poetic words used, you're expected to be familiar with such games already, so, if it includes kanji, no furigana, if it's an RPG mainly aimed at kids like pokémon everything is in kana with spaces. But I think the new pokémon games can switch to kanji, too, and again, no furigana.