London has the fifth most Michelin stars in the world. It's only one place behind New York. It certainly has far more than San Francisco. You can get cuisine from anywhere in the world in London, including many outstanding British cuisine restaurants.
That's not a valid argument. It's one of the most populous modern cities. That's like saying a city has a great music scene because it's top 5 based on Grammy winners. You know London and food is not a thing.
Even if you went w Michelin stars, London w almost 9 M population has 85 and San Fran w less than 1M has 75. San Fran is known for good food. London is not.