DSLRs still have the best performance and are cheaper than interchangeable lens compacts (ILCs), probably due to their less compact bodies. There is more to a DSLR than its mirror and viewfinder. While smaller cameras have to rely on a contrast detection system for autofocus, DSLRs have a more accurate and faster phase detection system. There's an explanation
here.
The performance of ILCs are improving and closing the gap, but they also fall behind DSLRs in burst shooting, weather sealing, and battery life. It's also easier to fit a larger sensor into a bigger SLR body, which results in better image quality. DSLRs have a bigger lens selection, and the bigger lenses are superior because they can hold more elements, have longer focal lengths and wider apertures.
There is definitely a place for DSLRs, but most people don't require that kind of performance.
In comparison, iPhones and other smartphones have miniscule sensors which cannot come near to matching the light sensitivity and image quality of a simply larger piece of silicon. It's also very difficult to generate a thin depth of field with a smaller light collecting area, and impossible with the tiny lenses on smartphones unless the subject is very close.
Point-and-shoots (or compact cameras) have made giant gains in sensor size recently because camera companies have to compete with smartphones. So the performance of some compact cameras are far better than smartphones, but they still don't match cameras with changeable lenses. However, compacts are
approacing that kind of
performance.
Most photographs I take now are with the original Sony RX100, one of the first cameras to fit a large sensor into a tiny body. The image quality from that little compact is close to a DSLR, but it lacks the lenses, battery life, depth of field control, and performance.
Smartphone:
http://fav.me/d7zlkug
2008 point-and-shoot:
http://fav.me/d6oz6fz
2012 point-and-shoot:
http://fav.me/d85jzpj
DSLR (shallow DoF):
http://fav.me/d4u0yn0
DSLR (wide DoF):
http://fav.me/d6eadg2