Great
Mr. Tambourine Man by The Byrds, 1965 (Bob Dylan)

Case Where Cover Is Better Than Original
Blinded By The Light by Manfred Mann's Earth Band, 1977 (Bruce Springsteen, 1973)

F for Fake - Amen! Devo and the Heads are two great examples. I'd like to add to that Devo's version of Working in a Coal Mine.

Also have to agree with Hollowgen's assessment of G n R's ruination of "Sympathy for the Devil", which in my opinion is one of the greatest rock songs ever.

My personal top pick for #1 all-time ruination remake:
The Fugees, who had the audacity to ATTEMPT a cover of "Bohemian Rhapsody".
A. They should have been hung, drawn, and quartered for that one.
B. Their manager should have been shot.
C. The record label should have had their business taken away from them for allowing that to be put on to a CD.

The Fugees - YUCK.

Props to the mention of The Pet Shop Boys. Any cover they do is innovative, musical and interesing. Their "Always On My Mind/Can't Take My Eyes Off Of You" medley is genius.

I thought it was "Where The Streets Have No Name/Can't Take My Eyes Off Of You." Or did they also record a medley of that song with "Always On My Mind"?

D'oh! You are correct.

Blasphemy!

Their covers of Loving Cup and Also Sprach Zarathrustra are incredible.

Buttmunker - This is where freedom of choice is a great thing. The version of "Blinded by the Light" by Manfred Mann is HORRIBLE in my opinion. Yes, I'm a huge Springsteen fan, but what they did that song was ridiculous. They butchered out a ton of the lyrics, and made it some cheesy, mainstream, pop song. I like the sound of the song, yes...but the fact that they cut it all to pieces ruined it.

Naimee Coleman's cover of The Cure's "Lovesong".

It'll play at my wedding someday.

Sometimes cutting a song in a cover version is essential in order to get it radio airplay. A good example would be Mr. Tambourine Man. Bob Dylan had his album version going over five minutes in length, but The Byrds used just one verse in their cover.

The reason Manfred Mann and The Byrds cut their versions down to size was to get it radio play - and perhaps, in a nobler cause, to get their favorite songs some attention to an audience that may not have picked up Springsteen's Greetings From Asbury Park, New Jersey.

Reminds me of a story - Nilssen covered the Badfinger song Without You, an album track that went unnoticed. Nilssen heard it one night, thinking it was John Lennon, and loved it. He later found out it was by Badfinger, and said: "That song deserves to be #1!" So he covered the obscure tune and, sure enough, Without You went to No.1 in 1974.

Homage.

Best:
Dune - Who Wants to Live Forever
Ahmet & Dweezil Zappa - Baby Hit Me One More Time

Heh.. I thought I posted my pick to this thread, I guess not.

I'd have to say that one of the worst covers I have ever heard was System of a Down covering Metro (Berlin)

HORRIBLE
Papa Don't Preach by Kelly Osbourne

Nobody Does It Better - Radiohead
Wish You Were Here - Radiohead
Everybody Here Wants You - Lewis Taylor
Electric Ladyland - Lewis Taylor
Mister Bojangles - John Holt

Has anyone mentioned
Good(an understatement)
All Along the Watchtower - Jimi Hendrix

Also I was listening to Bob & Tom the other day and they were saying someone conducted a poll somewhere(forgot the details) wondering what the worst Beatles cover song of all time is.... the poud winner...er loser... William Shatner doing Lucy in the Sky with Diamonds. Then they proceded to play some. Wow. My ears just wanted to bleed.

VERY Good
Memphis, written by Chuck Berry
It was never a hit for Chuck Berry, but it was written I suppose as an album cut before his incarceration in 1959.

1) Lonnie Mack covered it in 1963 as an instrumental, and took the song to #3.

2) Johnny Rivers covered it just a year later, with full vocals, and took the song one notch higher (#2 for two weeks in 1964)

This is probably the only case where the original artist didn't have a hit with his own song, but had two separate artists cover them successfully, in two different genres.

This is a case where the original artist, Peter Frampton, didn't do as well on the charts with his song when compared to the artists who covered it.

1) Peter Frampton took it to #12 in 1976.
2) Will To Power took it to #1 in 1988 (as mentioned above).
3) Big Mountain took it to #6 in 1994.

THE WORST...

Mariah Carey - Def Leppard's "Bringin' On The Heartbreak"

I wanted to jab pencils in my ears after hearing this!

Better
Barbara Ann by The Beach Boys, 1966 (The Regents)

Great
All written by Bob Dylan:
Blowin' In The Wind by Peter Paul & Mary, 1963
It Ain't Me Babe by The Turtles, 1965
Mr. Tambourine Man by The Byrds, 1965
The Mighty Quinn by Manfred Mann, 1968
All Along The Watchtower by Jimi Hendrex, 1968

The Thief by Can covered by Radiohead. "Why must I be the thief?"

One that I listen to at work that always gets people is:

Billy Joel - Shameless

The reaction is always the same. Who is that singing Garth Brooks' song?

The most successful Top 10 Beatles cover tunes were the ones never released themselves.

1. Lucy In The Sky With Diamonds #1 for two weeks by Elton John, 1975
The Beatles never released any singles from their 1967 album Sgt Peppers Lonely Hearts Club Band, although the tune was very popular.

2. You Won't See Me #6 by Anne Murray, 1976
From Rubber Soul (not released as a single)

3. You've Got To Hide Your Love Away #10 by The Silkie, 1965
From Help

Best : The Corrs , SRV - little Wing

Worst : Staind - Sober

One that doesn't seem to have been mentioned yet but IMHO is better than the original even:

Bryan Ferry - Jealous Guy

Best : 'Open Arms' and 'Bringin On The Heartbreak' by Mariah Carey

The Good:

Bruce Springsteen "Trapped"
The Replacements "Black Diamond"
Johnny Cash "Hurt"
Jimi Hendrix "All Along the Watchtower"
The Byrds "Mr. Tabourine Man"
The Byrds "It's All Over Baby Blue"

The Bad and the Ugly:

Puff Daddy "Kashmir"
Madonna "American Pie"
Lenny Kravitz "American Woman"
Celine Dion "I Drive All Night"