Star Trek: The New Cast vs. The Original

Dr. Leonard "Bones" McCoy

Now: Karl Urban
This New Zealand-born actor is no stranger to fantasy. He's best known for playing Eomer in the second and third installments of the Lord of the Rings trilogy and his role in the Viking adventure Pathfinder. He also played a Russian assassin in The Bourne Supremacy and starred in the big-screen adaptation of the computer game Doom.

Then: DeForest Kelley
Kelley never got out from under his role on Star Trek, and despite a few other TV and movie gigs, basically went into retirement. He did take up poetry, and published two books of his work before dying of stomach cancer in 1999.