Eh ... "equal or better" ? Come to think of it, just "different" could be justification enough, wouldn't it, Mark ?... To be honest I'm having a very hard time trying to come up with a song that I would want another artist to do that I feel would be equal or better. Otherwise what's the point right?
But I agree that singling out an artist seems to need some heavy thought, and heavy thought is way beyond me :S
Since I must go down an easier road, there's also the possibility of wanting to hear a song in a different style, like: ... Bluegrass !
Pierre