2D side view its really something that can take anyone to despair. The only way it makes sense is if the player is moving inside a complex or a big castle.
Trying to do a big city in a 2d side scrolling game, and all of a sudden your brain starts to realize that pedestrians dont walk on roof tops, and there is no way of making paths leading the player up or down.
It takes a lot of eye deceiving and short camera angles, to give the player the impression is walking on a big city.