Alanis Morissette would consider that ironic.
mmm
Especially since there’s no I either?
Allison, Mose
Beatles
Cohen, Leonard
Dylan, Bob
Edwards, Jonathan
Fairport Convention
Griffin, Patty
Havens, Richie
Incredible String Band
Jethro Tull
Kinks
Lazarus (folk trio, not metal band)
Mitchell, Joni
Nyro, Laura
Ochs, Phil
Pentangle
Renbourn, John
Steeleye Span
Traffic
Van Ronk, Dave
Wonder, Stevie
Young, Neil
Zombies
Stage names and not birth names, I presume?
(Elton John, not Reginald Dwight; Bob Dylan, not Zimmerman, etc.)
My Sophie’s Choices:
Picking Paul Simon over Steely Dan.
Picking Jack White over the Who.
mmm
Tori Amos
Billy Bragg
Cocteau Twins
Dead Can Dance
Einsturzende Neubauten
the Fall
Peter Gabriel
Imogen Heap
Inspiral Carpets
Joy Division
Killing Joke
Lush
My Bloody Valentine
New Order
Sinead O’connor
Pixies
Queen
Red Hot Chili Peppers
Shelleyan Orphan
This Mortal Coil
Underworld
Velvet Underground
Wolfsheim
Xymox
Yazoo
John Zorn
Safe to say you like prog and hard rock/metal. 
I don’t think I’ve seen X the band (Exene Cervenka’s vehicle) yet.
Yep, I’m invisible. 
Allman Brothers Band
Beatles
Clapton, Eric
Dylan, Bob
Emerson, Lake & Palmer
Fleetwood Mac (Peter Green era)
Genesis (Gabriel/Hackett era)
Hackett, Steve
Isley Brothers
Jethro Tull
Kinks
Led Zeppelin
Mott the Hoople
Neville Brothers
Outlaws
Pink Floyd
Quicksilver Messenger Service
Rolling Stones
Steely Dan
Traffic
Uriah Heep
Vaughan, Stevie Ray
Who
XTC
Yardbirds
Zombies
N and U were definitely the toughest for me
Picking Mahler over Mozart.
Haydn over Handel.
Szymanowski over Strauss (Richard).
Red Allen over Louis Armstrong.
Chet Baker over Count Basie.
Monk over Mingus.
Bird over Art Pepper.
Also Bach over Beethoven, Brahms, and Bruckner…but not really, 'cause I couldn’t live without me Bach.
My X was X.
I was going to play along until I realised there are so many great artists whose name starts with “B”.
My instinctive choice would have been Bowie. But then, there’s Kate Bush. And The Beatles. No way I can chose between those three.
Never mind, I’ll do Classical composers. That’s easy: Brahms. Oh wait, there’s Beethoven, too. Well, if push comes to shove, I can pick the former. S**t, I forgot Bach. Impossible to pick one over the other :(.
Correct.
mmm
Ayreon
Black Heart Procession
Charlemagne
Dead Kennedys
Epica
Flaming Lips
Glass Hammer
Hammerfall
Ida (band was named after someone’s grandma I think)
Judas Priest
Kamelot
Lana Lane
Mercury Program
Nightwish
Ozzy Osbourne
Pinetop Seven
Quasi
Rhapsody (which is now known as Rhapsody of Fire)
Stream of Passion
Tarja Turunen
Ugly Cassanova
Vision Divine
Within Temptation
Young Fresh Fellows
Missing X and Z. Could have went Frank Zappa but I don’t own any of his music and am not that familiar with it.
Apple, Fiona
Bjork
Chvrches
Dolphy, Eric
Eve
Furtado, Nelly
Grimes
Hubbard, Freddie
Imbruglia, Natalie
Jones, Tom
Kronos Quartet
LL Cool J
Morricone, Ennio
Nine Inch Nails
Oswald, John
Piazzolla, Astor
Quinteto Real
Rey, Lana del
Swizz Beatz
Thunders, Johnny
Uncle Tupelo
Veronicas
Waits, Tom
XCX, Charli
Yeah Yeah Yeahs
Zorn, John
I’m actually pretty happy with the way the list turned out, even though I cheated once…
Alice Cooper (‘A’ because it’s the band name, later retconned as the individual Alice)
Blue Oyster Cult
Concrete Blonde (tough one, a lot of ‘C’ love)
Dolby, Thomas
EMF
Frankie Goes to Hollywood
Garbage
Hendrix, Jimi
Iron Maiden
Jethro Tull
Kottke, Leo
Love & Rockets
Moby (so many 'M’s, a dozen favorites here)
Nena
Oingo Boingo
Pink Floyd
Queen
Ramones
Sisters of Mercy (don’t make me choose, why do I have to choose!)
Transvision Vamp
Up With People (my only blank letter, just avoiding defaulting to U2. It’s a joke, really! Don’t hit me!)
Van Halen
White Stripes
XTC
Ylvis
The Zombies
This was harder than I thought. Turns out there a artists I like that start with the same letter, so filling in the blanks took some work :
AC/DC
Beastie Boys
Cheap Trick
Def Leppard
Enuff Z’Nuff
Foo Fighters
Ghost
Heart
Incubus
Judas Priest
Kiss
Led Zeppelin
Motley Crue
Nine Inch Nails
Ozzy Osbourne
Pantera
Queensryche
Rage Against The Machine
Soundgarden
Theory Of A Deadman
UFO
Van Halen
White, Jack
Kings X (don’t have any other X’s in my collection, sorry)
Yardbirds
ZZ Top
Aerosmith
Beatles
Crosby, Stills, and Nash
Doobie Brothers
Eagles
Fabulous Thunderbirds
Guy, Buddy
Heart
Isley Brothers, The
James Gang, The
King, Albert
Little Feat
Mason, Dave
Nilsson, Harry
Outfield, The
Petty, Tom and the Heartbreakers
Quicksilver Messenger Service
Russell, Leon
Santana
Temptations, The
U-2
Vaughn, Stevie Ray
Who, The
X - ?
Young, Neil
Zevon, Warren
These are purely off the top of my head, so I may be leaving out someone I will be sorry I omitted later, but I am still good with this list.