Clean them up and get rid of the pedophiles and gangs that hang out in them. Paint over the graffiti and make it a serious crime for defacing public property.
If the parks are safe clean then people will use them and enjoy them.
I would also add more BBQ pits and picnic tables. I would also let people that are adults bring alcohol in the parks if they choose. I remember back in the 80's we use to play softball and had a few beers and just had fun. But now you can't do that, so we stopped playing softball.