The physical similarities between Portland and Jacksonville are really obvious. A similarly scaled river runs through the middle of town and is the major asset to the city's central core.
But - Jacksonville will never be Portland - and the differences are systematic and culturally ingrained...
1. Portland has a more educated population, which demands forward-thinking & innovative leadership.
2. Portland has multiple significant & well-regarded colleges and universities in it's city (Portland State, Univ. of Portland, Lewis & Clark State, Reed College, etc.) which further adds to the intellectual make-up of the city.
3. Portland emphasized environmental consideration long before it was commonplace or popular. Consequently, they have given their most valuable/sensitive land to public/civic use, and have respected the value of land by managing unfettered growth and sprawl.
4. Portland demonstrated a commitment to quality public transportation. It is a viable (desirable) option for all segments of the population through all age, income, and demographics. Great urban/suburban neighborhoods are linked to downtown by light-rail & bus (Eastmoreland, Beaverton, Gresham, etc.). This would be like Deerwood, San Jose, Riverside, Avondale, Ortega, Springfield, and Ponte Vedra being efficiently connected via light rail.
5. Portland has a respectable public educational system - not perfect.
6. Portland does not suffer from the same degree of civil rights "hangover" as is found so prevalent in the south, which manifests itself in obvious and not so obvious ways.
7. Portland has a great climate (but they'll never admit it) for outdoor recreation - and has made the public investment to promote biking in the urban environment. Refer back to #3.
8. Portland made a great commitment to urban parks - which has created positive public activity downtown, and gave the ENTIRE downtown riverfront to the public, which translated into enhanced value deeper into the downtown core.
The differences aren't about preservation of individual or a collection of individual historic buildings, or even a particular development pattern. The biggest difference is the mentality - which, unless you've lived both places - it's not possible to understand how broad the gap is...