The plant in the photos looks like an Alberta spruce. This is native to Canada and the Northern U.S. Grows best in full sun and moist soils but not wet ones. It does not like a lot of stress. Reasons for branch dieback include poor drainage and/or spider mites, an insect. http://extension.umd.edu/hgic/spider-mites-trees-and-shrubs
You can check for this.
The tree will not revert to its former glory.
Since these plants are located in a prominent location of your landscape, we recommend replacing with another type of plant. Perhaps a low growing holly.