I'd have to say 3 green spaces. Albert is right - Prospect Park and the Botanical Gardens for sure, but Greenwood Cemetary is a big green space as well. It's not a gloomy place, nor was it ever. Before there were parks, Victorian people picnicked in the cemetary and enjoyed the foliage and the statues. There are many notable people buried there. There are concerts held there and some great themed walking tours. I once went on a Halloween walking tour visiting the some of the more notorious long-term residents. Also notable is that the cemetary is the only part of Brooklyn that retains its original form - never leveled or artificial slopes put it. It's the way it was since the beginning of time.
Halstead Property, LLC