There is nothing wrong with urban sprawl.
But if you want people to move back into cities then simply lower the taxes. That is why people are leaving cities.
Develop green spaces around the perimeters of urban centres (easier said than done) and build up as opposed to out (condos or even semi-detached take up less space than a single family dwelling. Then there is the whole issue of public transit and traffic but thats another day.
Zoning residential areas within city centers, security as in CC cameras and convenient public transit such as a PRT system.
Death threats.
