Three bands, one stage, one concert ...

As far as the best three I've ever seen on one bill, G'N'R, Metallica and Faith No More.

 

Let's see....
I saw Slipknot, Slayer and Sepultura together at Tattoo the Earth. Great show, I remember some of it well.
I saw Pantera, Ozzie and Black Sabbath on the first Ozzfest tour, that was cool.

Now that I have grown and not quite as angry, who would I like to see the most together are
DEAD: Long Beach Dub Allstars, Sublime, Bob Marley
Alive: Matisyahu, Jurrasic 5, Long Beach Dub Allstars
I have a thing for that mellow rasta sound these days.

 

Impossible dream trio: Uncle Tupelo/Gram Parsons/Lynyrd Skynyrd
Impossible dream trio2: Thin Lizzy/Alice In Chains/Pantera

Of acts that are still around: Black Keys/Drive-By Truckers/Gov't Mule

 

Dream: Allman Brothers (w/ Duane), Grateful Dead (w/ Jerry), Zeppelin

Still around: Jack Johnson, Jimmy Buffett, DMB

 

Uncle Tupelo, Sun Volt, Wilco. In that order. Saw the No Depression boys in their last show before their finales in St. Louis. Methinks the personalities will never let the twain meet.

 

Moddy: I knew there was a reason I liked you.

Saw CDB, Tucker and (the original) Skynyrd together on New Year's Eve '75/76. Awesome.

 

Zeppelin, Beatles, Simon and Garfunkel.

 

I actually saw Mos Def, Cypress Hill, Public Enemy, Wu-Tang and Rage Against the Machine, in that order, about a month ago. It was fucking amazing, and I don't even like hip-hop.

As for the dream: The Ramones and Social Distortion opening for Pearl Jam.

 

Sonic Youth, Wilco, Radiohead

 

The Alarm. Simple Minds. U2.

Die Happy!

 

Best three-band sets I've been lucky enough to see:

Andrew Dice Clay, Guns 'n' Roses, Metallica, 1992 (Motorhead was the first band, to a largely empty Rose Bowl).

Anthrax, Rob Zombie, Judas Priest, Halloween 2005

And as Faithless mentioned, the top three of Slayer, reunited Judas Priest and Black Sabbath was great at the 2004 Ozzfest. Was going to correct Precious Roy on the Ozzfest Tour point, since the first Ozzfest in 1996 had a top three o Danzig, Slayer and Ozzy . . .but that was only a few dates, not a major tour.

Had tickets in 1994 for Suicidal Tendencies, Alice in Chains and Metallica (when still in their prime, pre-Load), but of course Layne Staley was in Heroin rehab and AIC was replaced at some dates by different bands.

As for all-time, knowing that each band will play for a LONG time and be excellent:

Led Zeppelin, Rush, Metallica, my three favorites in ascending order

If it has to be bands we haven't seen, but that we know should be good (Beatles played in an era when they played for 30 minutes):

U2, original Van Halen, Led Zeppelin

 

That's a dang good list of three favorites.