IMHO developers time would be best spent making games tailored to the hardware they have. Let's face it, smartphone processing horsepower will always be generations behind desktop, plus interface limitations, plus screen size, etc. If they want make smartphone games and make money at it they need to make games that are tailored to the small form factor and power restrictions of the device rather than trying to port over games that "sound good" but "play poorly" because they were originally meant for the desktop.
I've purchased some of these ports for my iPhone, especially id software's stuff. I am sure they sell like hotcakes because of id's name alone. There have a great WOW factor but no lasting playability. It's always like "Why the hell am I playing this on a phone when I could actually be enjoying playing this on my desktop instead of fighting the limitations of the phone?"