My three nominations:
- “Life is a Rock” by Reunion
- “End of the World” by REM
- “We Didn’t Start the Fire” by Billy Joel
Others?
Everything on the (incredible, mind-blowingly awesome) Fu-Schnickens albums F.U. Don’t Take It Personal and Nervous Breakdown. No rapper, alive or dead, has ever had such an amazing ability as Chip Fu. Each song contains approximately 100,000,000 words (my rough count).
Oh okay, you just want one song?
What’s Up Doc? (Can We Rock) by Fu-Schnickens
Lose Yourself - Eminem
Blinded by the Light. The Manfred Mann cover rather than the Springsteen original.
What’s that one song by the Bare Naked Ladies?
One Week?
The Remedy ( I won’t worry my life) by Jason Mraz
“I’ve Been Everywhere,” Johnny Cash
Mr. Bad Example - Warren Zevon
I was gonna say that one. In my speech class last year, we had to do a lip sync (So we would move our mouths more when giving a speech, or something like that). I did that song. That was fun.
Also, what about American Pie?
Tokyo Storm Warning - Elvis Costello
For sheer tongue-twisting rapid-fire lines that never seem to end (if not total word count per se):
“African Night Flight” – David Bowie
"Burning With Optimism’s Flames – XTC
“Sailor and Widow” – Keren Ann
“Crosseyed and Painless” – Talking Heads
Honorable Mentions:
“Turning Japanese” – The Vapors
“The Gift” – The Velvet Underground (laconic delivery, but it goes on forever)
“Neurotica” – King Crimson
“Albuquerque” and “Genius in France” by Weird Al 
Cash may have covered it, but the song is by Hank Snow.
What’s the OP looking for? Most words, period? Most rapid delivery of words? If it’s just most words, there’s probably some really long songs that qualify. Jethro Tull have two albums which could be classified as one long song each, “Thick As A Brick” and “Passion Play.”
For rapid delivery, Freddie Mercury’s got some good bits in “Stone Cold Crazy”, and They Might Be Giants do a pretty fast bit in “Letterbox.”
thwartme
Arlo Guthrie’s Alice’s Restaurant has quite a few words in it, as well as 8x10 glossies with circles & arrows.
Not to mention a pretty fast riff where the sergeant talked for 45 minutes and nobody understood a single word he said.
“Subterreanean Homesick Blues” by Bob Dylan
If it’s the former, I’m sure some Grateful Dead songs belong on the list. “Wordy” fits what I’ve heard from Robert Hunter. If it’s the second, something from Blues Traveler has to fit.
Tom Waits “Step Right Up”