Best covers

I'm sure there's a bunch more, but these are some that I think are better than the originals, off the top of my head...

 List with video links

Cold - Space Oddity (David Bowie)
Obviously not the correct video, but only thing I could find with the song with 5 secs of effort :-P

 Spoiler

[youtube]2BVpAnZi_oU[/youtube]

Godhead - Eleanor Rigby (Beatles)

 Spoiler

[YOUTUBE]br2a0iKn_JA[/YOUTUBE]

Evan's Blue - Possession (Sarah MacLaughlin)

 Spoiler

[youtube]2Q1VOcU089Y[/youtube]

Evan's Blue - Caught a Lite Sneeze (Tori Amos)

 Spoiler

[youtube]2m4CBruixM8[/youtube]

Emil Bulls - Take on Me (a-ha)

 Spoiler

[youtube]mtJH2bMesfc[/youtube]

Celestial Season - Vienna (Ultravox)

 Spoiler

[youtube]D_RZBKfQVcw[/youtube]

Vanilla Ice - Too Cold (lol.. he covered himself and totally remade Ice Ice Baby)

 Spoiler

[youtube]zvtDiPt6s24[/youtube]

 List without videos because they're too well known and I'm lazy

Hendrix - All Along the Watchtower (Bob Dylan)
Johnny Cash - Hurt (NIN)
Metallica - Turn the Page (Bob Seger)
Metallica - Whiskey in the Jar (Thin Lizzy, I think?)
Metallica - Tuesday's Gone (Lynyrd Skynard)
Disturbed - Land of Confusion (Genesis)
Disturbed - Shout (Van Halen)
A Perfect Circle - Imagine (John Lennon)
System of a Down - Dammit (Blink 182)
Red Hot Chili Peppers - Higher Ground (Stevie Wonder)
Guns n' Roses - Knocking on Heaven's Door (Bob Dylan)
Guns n' Roses - Live and Let Die (Paul McCartney?)
Pearl Jam - Last Kiss (not sure, but it is a cover)
Gary Jules - Mad World (Tears for Fears)
Nirvana - The Man Who Sold The World (David Bowie)
Nirvana - Lake of Fire (Meat Puppets)
Nirvana - Jesus Don't Want Me For a Sunbeam (Vaselines)
Nirvana - Where Did You Sleep Last Night(Leadbelly)
A whole slew of Apocalyptica songs
Dynamite Hack - Boyz in da Hood (not sure who did the original)
Finger 11 - Walking in My Shoes (Depeche Mode)
In Flames - Everything Counts (Depeche Mode)
Limp Bizkit - Faith (sorry, but George Michael's original just sucks...)

... and I'm out of ideas, as is obvious by that last one. It IS better than the original, though I'm sure I could come up with more if I was at home and could check my music library.