Switch Ships 129.53M as of June 2023, Zelda: Tears of the Kingdom at 18.51M

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I wouldn't underestimate Wonder.
Being 2D can make it more accessible to casual audiences, and gives it nostalgic appeal to the tens of millions who grew up with the old SMB games.
If it's well made enough to generate positive word of mouth, over 30 million is definitely achievable.