I live in New England and am looking for trees to fill in the
openings my neighbor just made in what I thought was good privacy.
The land is non-useable wetlands but we do have maples growing it.
Does anyone have any suggestions as to what trees/bushes I could
plant there to keep my privacy? The town planted evergreens about
6 years ago and they are just about dead now.

Look into Leyland Cyprus to see if it grows in your zone.

Otherwise I'd go with Red Maples.

Dick