I think this as many other things are highly subjective.
One might say that something that could be considered a fairly good indicator of a "good" food-scene would be this: https://www.statista.com/chart/16308/michelin-restaurant-us/
Where SF is no 2 in the country for number of Michelin star restaurants.
Again as the first sentence states; one might argue this is not the indicator of a "good" food-scene but I guess we'll have to take what we can in terms of objectivity to try to judge a city on different things, and for food this is at least for high earners, probably a somewhat good indicator.
One might say that something that could be considered a fairly good indicator of a "good" food-scene would be this: https://www.statista.com/chart/16308/michelin-restaurant-us/ Where SF is no 2 in the country for number of Michelin star restaurants. Again as the first sentence states; one might argue this is not the indicator of a "good" food-scene but I guess we'll have to take what we can in terms of objectivity to try to judge a city on different things, and for food this is at least for high earners, probably a somewhat good indicator.