The second generation iPhone was the first as you know them today. The first was a glorified iPod Touch with a cellular radio stack. In fact, aside from the better touch-friendly screen, the iPhone was a step backwards from Windows CE/Smartphone/Mobile devices because on those I could run applications.

Source: I owned Windows CE/Smartphone/Mobile devices starting with the Samsung i600 and was actively using a Treo 700w when the iPhone was released.