It kinda depends on my mood and what I’ve been listening to most at a given time, but I’d say the most enduring song would be:

• “(Don’t Fear) The Reaper” by Blue Oyster Cult. I have been listening to the Tom Rhodes cover recently and have really like it as well, but I don’t think it quite tops the original.
• “The Man Who Sold the World”. I’m not sure which I like better, the original by David Bowie or the cover by Midge Ure.