I think it's interesting that Ruskin and Berger were the first two that I thought of too. If we'd both named three
painters I think it's much less likely that we'd have picked the same ones, because there are so very many of them to choose from.
I should add (it doesn't make me look great, but does bolster the case I'm agreeing with here) that more precisely my first two names were John Ruskin and John, oh damn it, what's his name, the "Ways of Seeing" guy -- and that I hadn't thought of a third name. (Perhaps with effort I could dredge one more out of my memory, but it wouldn't be Walter Benjamin because I confess I don't recall hearing of him.)
There just are a lot more famous artists than famous art critics. (And, as you say, the same for music.)