Top Ten Most Played Artists in Your iTunes Library:
(I can't do it based on most-played, because I don't keep play counts, but I can estimate the ten most-represented artists, which are thereby the ten most played...in no particular order, probably)

1. Nine Inch Nails
2. Toad the Wet Sprocket
3. Tool
4. the Goo Goo Dolls
5. Soundgarden
6. Bryan Adams
7. U2
8. Pearl Jam
9. Incubus
10. Metallica

What was the first song you heard by 6? (Bryan Adams)
I have no idea. I'm sure I heard many before I actually started to listen and have an opinion.  And even when I was ten and I bought a Greatest Hits compilation of his, I was surprised that I already knew almost all of the songs but hadn't known them by title/artist before.

What is your favorite album by 2? (Toad the Wet Sprocket)
They don't even have very many, and that is still not a fair question.  They're all so different!  I probably have to say "Coil."  It's very dark and depressed, yet has some of the best songs, one of which is the first song I remember identifying with the band by name and getting excited about when I heard it on the radio. (Although when I later went and bought the previous albums, I found plenty more songs I already knew).

What is your favorite lyric that 5 has sung? (Soundgarden)
"I'm a searchlight soul they say, but I can't see it in the night/and i'm only faking when I get it right."
"So don't you lock up something that you wanted to see fly/Hands are for shaking/No, not tying." (both from the same song)

"Give me little bits of more than I can take."

"Break, if you like sound/if it gets you up/if it brings you down...Hate, if you wanna hate/if it keeps you safe/ If it makes you brave."

How many times have you seen 4 live? (GGD)
Three.  A good one to end up with on this question, since I haven't seen many of those listed live)

What is your favorite song by 7? (U2)
"Love Comes Tumbling," "Wire," or "Hold Me, Thrill Me, Kiss Me, Kill Me."

What is a good memory involving the music of 10? (Metallica)
This is not exact, but "Fade to Black" reminds me of being a little kid. I can't remember a time when I didn't love that song, even when I was too young to understand it.

Is there a song by 3 that makes you sad? (Tool)
No, there's really not.

What is your favorite lyric that 2 has sung? (Toad the Wet Sprocket)
"It's hard to rely on my good intentions/When my head's full of things that I can't mention/It seem I usually get things right/But I can't understand what I did last night."

"Did we expect these things to change/by waking up and suddenly there they are?/All I need's a starting place/And nothing ever seemed so hard."

"Nothing's so loud as hearing when we lie/The truth is not kind, and you said neither am I."

How did you get into 3? (Tool)
Jaxon played a song he loved all the time on MMR, and I loved it too. So I listened to more.

What was the first song you heard by 1? (Nine Inch Nails)
Um, well, the first song I heard was probably "Head Like a Hole," because that's been around a very long time, and it was one of only a few that I knew until more recently.

What is your favorite song by 4? (GGD)
"Here is Gone" still takes it.

How many times have you seen 9 live? (Incubus)
One.

What is a good memory involving 2? (Toad the Wet Sprocket)
Wow, there are a lot of #2 questions.
March 4, 2003.

Is there a song of 8 that makes you sad? (Pearl Jam)
"Light Years" makes me sad sometimes, but it's probably my favorite PJ song, so usually not.

What is your favorite album of 5? (Soundgarden)
Probably "Superunknown"

What is your favorite lyric that 3 has sung? (Tool)
I pay less attention to the lyrics in Tool songs...but...

"I wanna feel the change consume me, feel the outside turning in
I wanna feel the metamorphosis and cleansing I've endured
In my shadow
Change is coming.
Now is my time.
Listen to my muscle memory.
Contemplate what I've been clinging to.
Forty-six and two ahead of me."

That's up there.  "The Pot" is up there.  And two songs by A Perfect Circle, the other band fronted by the singer of Tool, has two songs that are pretty much perfect and amazing.  "Weak and Powerless" and "The Hollow."  But I'm not putting three more whole songs here.

What is your favorite song of 1? (Nine Inch Nails)
Could you ask me a harder question?
"Head Like a Hole." "Wish." "Hurt." "I Do Not Want This." "Dead Souls." "Somewhat Damaged." "Into the Void." "The Hand that Feeds." "Only." "Sunspots." "Every Day Is Exactly the Same." "Capital G." 
Okay, that's enough.

What is your favorite song of 10? (Metallica)
"Nothing Else Matters." "Of Wolf and Man." "Welcome Home (Sanitarium)." "Fade to Black."

How many times have you seen 8 live? (Pearl Jam)
Hahaha...none yet.  But in a month I'll be seeing them twice.

What is your favorite album of 1? (Nine Inch Nails)
"With Teeth," only because of its appropriateness in my life at the time it came out.

What is a great memory you have considering 9? (Incubus)
Going to see them with Jeff. 
And the first time I ever really listened to the words to "Dig."

What was the first song you heard by 8? (Pearl Jam)
I can't possibly know the answer to that.

What is your favorite cover by 2? (Toad the Wet Sprocket)
I don't think I've ever heard them do any.