There are many ways to improve your cityscape shot but the fastest way to add that additional punch to your image is by using Nik's Color Efex Pro. Let me start off by saying I'm not in anyway affiliated with Nik Software nor do they pay me anything. I just love using their products.
So here is my cityscape shot from the TV Tower in Sapporo. It already looks ok but it could use a little bit more pop.
I can go into Lightroom and play with the HSL and/or saturation sliders. I could also do the same in Photoshop with adjustment layers. But these steps require extra knowledge and effort to make the image pop out even more. So the elegant solution is to use the Skylight Filter of the Color Efex Pro. Just select the filter, vary the strength to your liking, press OK and tadaa...
Here is the final image, you can hover over just to check how the filter helped improve the image (in my opinion). I find the Skylight Filter very effective for night photography and not so with daytime because it warms the image too much.
Here are additional images that used the same filter. Try it and tell me what you think :)