Most listened to artist

Just a guess. Ask me tomorrow, I might have a different answer...

Allman Bros. 

The Band 

'70's Grateful Dead

Chick Corea

John McLaughlin 

Joni Mitchell

EC (with J. Mayall, Cream, B.Faith, D. and the Dominos)

Acoustic Wayne Shorter (not Weather Report)

Bobby Hutcherson 

McCoy Tyner

Ry Cooder

Yeah, I’m old, too. And I can’t count, either...   ;o)

In no particular order:

The Cure

Depeche Mode

Delerium

Alex Cortiz

Bob Marley

Skinny Puppy

Steely Dan

Eagles

Bob Seger

Eagles

Lester Young

Duke Ellington

Sun Ra

Miles Davis ( esp. electric stuff)

Bill Evans

Chet Baker

Eno (Mostly 70’s stuff including early Roxy)

Velvet Underground/Lou Reed

BOWIE

Stones

Genesis (old stuff )

 Pink Floyd

Jethro Tull

Dire Straights / Mark Knopfler

Yes

Grateful Dead

CSNY and their before and afters

Steely Dan

Moody Blues

Jackie Greene

I will have a very hard time narrowing it down to just 10, since I listen to 3 main genres of music, and each one has bands, musicians, composers that I have probably listened to at nearly equal rates. 

So, I am going to "cheat" (one list per genre):

Prog:

Yes
King Crimson
PFM
Magma
Banco
Gentle Giant
Genesis
Frank Zappa
Univers Zero
Pain of Salvation

Jazz:
John Coltrane
Allan Holdsworth
Mahavishnu Orchestra
Return to Forever
Steve Coleman
Anthony Braxton
McCoy Tyner
Keith Jarrett
Oregon
Jean Luc Ponty

Classical:
Elliott Carter
Joan Tower
Bruno Maderna
Charles Wuorinen
Arnold Schoenberg
Gyorgi Ligeti
Krzysztof Penderecki 
Bela Bartok
Igor Stravinsky
Kaija Saariaho