I think I like this one more than the one with the jets, but the jets one is cool too for its sense of movement and more details. It's a tough decision.
I saw a nice tut here on DA You just duplicate the layer, sharpen few times, desaturate, adjust levels to that amount of city lights you need and then set to screen/color dodge/linear dodge - that's it This works great for small planets, for big ones - not always. In this work I've used both this technique and photo manipulation of actual city lights
Nice work
You just duplicate the layer, sharpen few times, desaturate, adjust levels to that amount of city lights you need and then set to screen/color dodge/linear dodge - that's it