Curves, histograms, levels, rotoscope, selections, applied image, colour balance, white balance ..... It's like a new language and like all new languages, photoshop gives you new ways to express yourself.
I struggled and failed with Pop India. Here's a review of some of my Indian photos. Photoshopped and unphotoshopped.
On this picture of a girl, it's easy to see the enhancement made by two curve adjustments, one for colour/contrast and the other for whitening the eyes/teeth.
The difference between these two pictures is more dramatic. I used a 'rotoscope' effect, which I think is very effective with urban scene (probably anything that is detailed). The non-photoshopped picture is a little flat and unsharp, which is easily remedied in photoshop with a little tweaking with 'levels' and 'curves'.