What do you suggest as my first DSLR?

At your budget, you're looking at an entry level camera. They're all good. They all have more than 7 megapixels. It can shoot track and field, but a prosumer model would be better because of a more sophisticated autofocus and higher burst rate. The entry level models will do fine with cityscapes, but you'll need a tripod for night shots. Note that your first camera will tend to lock you into the brand. That's because already having at least one lens will compel you to buy your second camera so that it can use the lens. That's why many recommend either Canon or Nikon, as they have the widest variety of the best lenses.