Man, there are so many and to me, the diff between a good ballad and a great one is the emotional connection. So by that criterion, the list is highly personal. A few of my favorites:
Nancy Griffith's cover of Townes van Zant's Tecumseh Valley
EmmyLou Harris- Most anything from Angel Band if you are counting gospel. Otherwise (and more contemporary), Broken Man's Lament or Kern River.
Richard and Linda Thompson- Bee's Wing
Jackson Browne- After the Deluge (not a traditional ballad but a ballad nonetheless, IMO).
Patty Loveless- You'll Never Leave Harlan Alive
Dimming of the Day- lots of covers; maybe Bonnie Raitt or Richard Thompson.
Eddie From Ohio- Minnesota 1945
Vince Gill- Pretty Little Adriana
Michelle Shocked- Anchorage
Nancy Griffith's cover of Townes van Zant's Tecumseh Valley
EmmyLou Harris- Most anything from Angel Band if you are counting gospel. Otherwise (and more contemporary), Broken Man's Lament or Kern River.
Richard and Linda Thompson- Bee's Wing
Jackson Browne- After the Deluge (not a traditional ballad but a ballad nonetheless, IMO).
Patty Loveless- You'll Never Leave Harlan Alive
Dimming of the Day- lots of covers; maybe Bonnie Raitt or Richard Thompson.
Eddie From Ohio- Minnesota 1945
Vince Gill- Pretty Little Adriana
Michelle Shocked- Anchorage