Size doesn't really matter, it's what's available in those cities. Megaton isn't big but serves it's purpose same goes for Bravil.
I agree. Skyrim could take place in one small room as long as that room has lots of intricate details in it, right?
I didn't think Bruma was all that big to begin with. Compared to some of the other cities, possibly. Hard to tell from a distant overhead view.
That's the point. Bruma was the smallest of the Oblivion cities, and Whiterun appears to be about the same size as it or smaller. Nine major Oblivion cities, five major Skyrim cities and one of the major Skyrim cities is smaller than the smallest Oblivion city.