Thank you all for reviving this. I must try some of the german folkmetal bands again.

If "The Morning Dew" is allowed, then I think the Nazareth version of it is the absolute killer.

Surely Lonnie Donegan's "Rock my Soul" was traditional gospel before he got at it?

I much liked Taj Mahal's version of Statesboro Blues.

Canned Heat did fine versions of many blues classics.

Do Robert Johnson originals count as "traditional" yet? If so Cream's version of "Crossroads", Fleetwood Mac's version of "Hellhound on my Trail" are both excellent - and the John Mayall version of "Dust my Broom/Blues" was a classic piece of updating.