I think you're mostly right about this. Aside from a few items, the south bay can match SF point for point. The big difference is that in the SB you need to know where those places are (they're not always obvious) and you have to drive many exits to get from one place to another.
For example, if I want hole-in-the-wall Mexican cuisine and I want some Vietnamese dessert, I might be able to walk from one place to the next, in SF. In SJ accomplishing the same would mean going from somewhere in north San Jose, to then somewhere on Senter road. There's no way to walk it (ok, 2 hours). If I want Cambodian it's another trek across the freeways. So, yes, things are there in the SB, but you have to know where to find them and they can be very far from each other. But, if you like "discovery" of hidden places, the SB has some interesting hidden in plain sight places. They're hidden because most have a very targeted (ethnic) audience and few people outside that audience tend to know about those places, unless intro'd by someone who knows.
That is to say, the 'ethnic' aspects of SF actually have a diverse audience in mind, while in SJ, for example, most of the ethnic aspects are directed to a select audience and thus are less approachable by outsiders. At least that's how I felt about these things when I was in SJ.