I think the SBCs are popular not only because they made so many, but just open something like a Speedway or Jeg's catalog and see how many people are making optional stuff for them. from intakes to headers, valve trains, cams, pistons, cranks, you-name-it, someone makes it for a small block. Usually quite a few choices in every category, like headers.
I have a friend who has built two nice Deuce roadsters with Ford 302 EFI powerplants, and he says the coupe he is building now will be a SBC. He made quite a colorful remark which I won't repeat about the relative power of the 302 vs a chevy.