Never got the love for Cash's "Hurt." It's really an awful piece and I prefer the original. Actually, I prefer the "quiet" version.
This is someone who freaking grew up on Cash.
But let's see the ones I prefer/like.
Someone already posted Disturbed's "Land of Confusion," And I love their version.
I'm a fan of the Dinosaur Jr cover of "Just Like Heaven" also posted, though I'm not sure I prefer it to the original. Manson's Sweet Dreams, and a lot of other staples.
Brian May's cover of "Hot Patootie" from the Rocky Horror Picture Show ranks up with the soundtrack version.
Freddie Mercury's "The Great Pretender" is better than the original.
The Stone Coyotes: "Paranoid," "Ace of Spaces," "It's Late" (Ricky Nelson). I always hated Ozzy's voice, so almost any cover'll do it. I also don't like Motorhead.
Johnny Hyde: Tainted Love. I like other covers, too, but I like his more than the Manson cover even.
Adam Lambert's "Mad Word."
Could probably go on for ages, but....