I’ve played neither Counterstrike nor Call of Duty, but I know de_dust2 by name and can even visualise what it looks like, and I’ve never heard of Rust or Nuketown.
If we count the Nuketown map on Call of Duty mobile (mobile has over a billion downloads) I would have to say that's the winner, but if not de_dust2 is the king. Mirage would also be pretty up there.
I think on the flip side, most of my brother's friends I played Call of Duty with probably haven't heard of counterstrike, or Quake, or unreal tournament.