The thrust of my argument is that there’s more of everything in a bigger city. As such you have more options and more competition.

The competition means that a lot of places scraping by in smaller cities can’t make it in a bigger city. In theory that means median quality is higher.

And even a 3-star restaurant won’t survive in a place that doesn’t get enough well-to-do visitors to sustain it.

For a more casual perspective, SF has 126 restaurants on the Michelin list (not all hve stars). My entire home country has 52.

None of this speaks to whether or not SF has more to offer you than other less dense cities in the US, so many of which have excellent restaurants and, indeed, better restaurants. I was very impressed with the food in Austin on a recent visit, for example. Perhaps if SF had continued on the high density curve while maintaining affordability (as Tōkyō has done) it would be a different story.

Quality food has more to do with agriculture and supply chains than money or density per se -- good salad is not something you can buy if no one is growing it -- and more and more areas in the US have made the transition to that kind of farming and production.

Now challenging SF on grocery stores -- that's another matter. They are drawing on deep roots, there.