What does 8-bit / 16-bit actually refer to?
Is it possible to identify games (by their graphics ?) as 8-bit games or 16-bit games or whatever bits games use nowadays?
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There is no set-in-stone definition of what "8-bit games" or "16-bit games" really means, so the answer to your question depends on your definition. See this related question.
In my experience, nowadays "8-bit" or "16-bit" usually refers to either the era in which the game was released, or its gameplay.