Satisfied diners.
Like I don't know what sort of grade or objective evaluation my mother would get, but she's an excellent cook, I think.
As for professional cooks, I can't really say, but I could taste a bounty of generosity in some of my best meal experiences. Some years ago, my brother's family came for the holidays. He's a foodie who once considered restaurateur for a career, and instead has become a bit of a dining snob. It was Christmas Eve, and he didn't want my home cooking for such an occasion. I told him, good luck finding a restaurant that's open. A bit of web searching, and he found one, owned by a TV celebrity chef. While dining there, my 2-yr old nephew at the time became fussy, crying and screaming. The chef came over to our table, made friends with the kid, picked him up, and gave him a tour of his back kitchen. My wide-eyed nephew returned calmed down and ate his Christmas Eve dinner with enthusiasm. The food was excellent! But, I ate wondering whether I might get a tour of his kitchen too, if I started a tantrum.