I agree with Steve, and also wanted to add a real biggie here;
Riverside didn't summarily tear down every vacant building, thereby creating a cost prohibitive situation for residents and businesses wanting to occupy the area. If there is little left to occupy, you're looking at the cost of building from scratch, which is a burden most restaurants, residential families, retail, etc., cannot afford. This is probably more responsible than any other one thing for the disparity in Riverside vs. Downtown, or even other historic neighborhoods that have failed to turn around like Springfield.
Preserving the properties is not only the ethically correct thing to do with regard to preservation initiatives, but it's the financially necessary component to an area ever being able to undergo a resurgence. 99% of people and small business can't afford to build from scratch. But they can afford to buy an old place and fix it up. When you remove this from the equation, the cost barriers to entry become too high, and so nobody does, with the result that the area suffers perpetual stagnation.