I have a line of 9 Leyland cypresses. 3 are dying and 3 are nice & green,...
It appears that your trees are failing to establish and were planted and or mulched too deeply. If they've not been regularly watered since they were planted it could also play a role.
You should be able to see the root flare, or widening of the trunk as it goes into the ground. Planted or mulched too deeply, roots can't get the oxygen they need and can die.
You only need 2-3 inches of mulch, and it should always be pulled back from contacting the trunk or stems of plants.
If the trees were balled and burlapped (as opposed to pot grown, be sure the wrap and cage were removed.
For the ones you think are still living (the first photo shows a pretty stressed plant- hope that's not one of the ones you described as 'green')
pull back mulch or soil to no more than 4 inches on top of the root system all around. Keep them deeply watered if we don't get rain.
You may or may not be able to save them- evergreens can hide damage for quite a while. (Think of a Christmas tree that is severed from its roots can stay green for many weeks, and sometimes months.)
If you replace, we'd recommend Arborvitae, which do better here in the long run, and here is our Planting Tips for Trees page: http://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/hgic/HGIC_Pubs/TreesandShrubs/...
This page shows common planting problems for trees and shrubs: