The Man Who Sold the World. I like Bowie, but I thought the unplugged music and Kurt's singing style suited the the song more.
Can't Take My Eyes Off You. Pretty much most covers sound much better to me than Frank Valli's original, don't really like his style.
Babe I'm Gonna Leave You. Joan Boaz's voice is just too sharp for me to enjoy. Plus, Zeppelin's version is the first I've heard. But the style between the two is so different it's magical.
And I thought that Muse's version of Feeling Good was almost as good as Nina Simone's original version, but Nina Simone's version is till better.