To me, it keeps changing.
The shops that sell electrical and electronic components (parts shops) mostly stick to the areas close to the station. These are the traditional shops of Akiba.
The more modern additions, like the maid cafes, phone/computer shops and adult goods shops, are on the increase. Newer shops have expended the area quite a bit.
The used games and videos shops are spread all around. It is sort of an adventure to go around and find a shop with what you want.
The bridge and the building seen in the station stamp used to be one end, but shops are now spilling over to the other side of the bridge.