That's a pretty bonkers statement. Cilantro is much more used worldwide (by about an order of magnitude). They look very similar, but don't taste anything alike. You might as well say basil is better than oregano. It's just not a very meaningful statement.

In a lot of the world flavor is about stacking complex flavors to get a melange of them. With the establishment of the top end of European cooking as French haute cuisine, there was instead an emphasis on simple, clear flavors. In that style, parsley, as a much more subtle herb, shines.