No, it is not knowledge of the city’s best dish, nor is it access to all the Yelp reviews, or even an understanding of how the spices in that cuisine work together.
I have a simple nomination. If you could only know one thing about a city, you would like to know what time the best and most popular restaurants fill up.
If you know that time, you can walk around a restaurant-rich area. Wait for the best places to start filling up, and then make your move and muscle your way through the door. Voila, the wisdom of crowds!
If you come too early, you cannot glean information from watching the customer flow because there isn’t any. If you come too late, the best places are already full, or they have lines which are too long. But if you are there at just the right time, and attentive to the movement of the crowds, what really can go wrong?
In Singapore the best time to start stalking the hawker centres is about 10:30 a.m., certainly no later than 11. Otherwise the lines at the best stalls are simply too long. Just show up at the right time, and assume the Singaporeans know what they are doing. It works. In Paris you must be looking for a good lunch restaurant before 12:30.
It is a common theme in food economics that knowledge of people, or knowledge of social mechanisms, is often more valuable than knowledge of food. Knowing whom to ask and also how to ask is also often more valuable than a detailed knowledge of a cuisine per se.