Siegel and Schuster were indeed from Cleveland, and the early strips did borrow from Cleveland for the look of Metropolis. Probably because that was the only big city the two teens were familiar with.
Metropolis evolved into an east coast city mainly because that was where the big cities were. The fact that all the major publishing houses, and large corporate headquarters were based in New York had a lot to do with it.
Metropolis was said to represent the more 'optomistic' side of New York, whereas Gotham was the darker version. In the early days of comic books they never considered using the names of real cities. Theirs was a fictional world that had fictional cities.
The Flash hailed from Central City, which most often was allied with St. Louis. At least until Keystone City became part of the same DC universe. Now one might consider those 'twin cities' to be Kansas City Mo, and Kansas City Ks.
Of course, Hal Jordan (Green Lantern) hailed from Coast City, which was the DC version of Los Angeles or San Francisco. Coast City was destroyed, but it got better.
Anyway, the main point is in the DC Universe, their fictional cities were never meant to actually 'be' a substitute for a real city, but they were reminiscient of a similar, corresponding city in our earth prime.
Tank (who wonders where Hobbs Bay is located in the Smallville version of Metropolis - which can be seen from a watertower in Smallville, Kansas)
