For a really serious answer in this order:
1. Guy Mariano
2. Henry Sanchez
3. Brian Wenning
Those 3 are legends and the majority of their skating is ledges. I feel Jesus Fernandez is up there but he's not as legendary as those 3, so I gave up listing more, it's too hard to say. There's plenty of legendary ledge skaters but they're also legends skating other stuff...like Chris Cole and Eric Koston for example.
Picking the best ledge trick of all time is too broad. Techest, longest, stylish, nose grind, back tail, nose blunt? You'd have to do categories. Maybe what video has the best ledge skating of all time, Mouse?