Well, yes. They can. And quite easily.
Recently, I ran across a great article (http://www.collectiveroots.org/benefits_of_parks) describing the economic, social and health benefits of parks. I'd encourage anyone interested in the topic to read it.
The basic idea, supported in the article by tons of academic research, is that people willing choose to pay more for a home located near a park. That's it. Simple, intuitive, and a truism that most successful realtors can readily confirm.
When people pay more for homes near parks, property tax valuations reflect this higher selling price, which in turn generates greater tax revenues. These revenues go on to increase the general coffers, repay bonds which funded the initial development, or finance ongoing park maintenance.
Homes near parks also tend to have higher re-sell values and tend to stay on the market for shorter periods of time. A 20% increase in the value of properties abutting parks is typical. Properties along greenways have documented increases in value of over 30%.
Bottom line, parks more than pay for themselves.