What are some covers that are much better than the original song?

Some that I can think of are:
Ted Kirkpatrick - War Pigs (Black Sabbath cover)
Impellitteri - Symptom of the Universe (Black Sabbath cover)
Audiovision - The Way (Stryper cover)
Biogenesis - Land of Confusion (Genesis cover)

I have a way-out-of-left-field opinion:
Judas Priest - Johnny B. Goode

This track slays!

Yeaup, Priest does the best covers:

"Green Manalishi With the Two-Pronged Crown" (live version preferred)

Deliverance - Sanctuary (Daniel Amos cover)

Johnny Cash - Hurt

(at least as good)
Holy Soldier - Gimme Shelter

Judas Priest - Diamonds & Rust 

...Probably the best example ever.  Also:

Queensryche - Gonna Get Close To You
Cirith Ungol - Fire
Celtic Frost - Mexican Radio
D.C. Talk - In The Light
Love Spit Love - How Soon Is Now


Other Great Covers That May Not Be Better, But I Like Them Just As Much:

Holy Soldier - Gimme Shelter
Fozzy - Stay Hungry
Killswitch Engage - Holy Diver
Metallica - Blitzkrieg
Red Hot Chili Peppers - Higher Ground
Coroner - I Want You (She's So Heavy)
P.O.D. - Bullet The Blue Sky
Pat Travers - Is This Love
The Lovemongers - Papa Was A Rolling Stone

Constantine wrote:Killswitch Engage - Holy Diver

This one raised my eyebrows, you’re saying a metalcore band is capable of matching Dio? I’m gonna have to see for myself if that’s true

Motley Crue - Helter Skelter

Deliverance - After Forever (but barely)

seth wrote:

Constantine wrote:Killswitch Engage - Holy Diver

This one raised my eyebrows, you’re saying a metalcore band is capable of matching Dio? I’m gonna have to see for myself if that’s true

I listened to it and it was actually pretty decent, although still nowhere near as good as the original imo

seth wrote:

I listened to it and it was actually pretty decent, although still nowhere near as good as the original imo

It's different.   I like what they did with it musically.