I was watching it earlier and it does appear that they pick their own songs, Ellen asked Aaron and he said yeah he picked it and a couple of others mentioned picking the songs too.
So, i'm guessing in "inspiration week" they pick a song from whoever has inspired them. When you look at it like that makes sense that MJ isn't on there, we can't expect him to have inspired every singer on the planet.
they have to pick from lists, and this is the list for this week!
* Your Love Keeps Lifting Me (Higher and Higher) – Jackie Wilson
* A Moment Like This – Kelly Clarkson
* Amazing Grace – Susan Boyle
* Angels – Robbie Williams
* Anyway – Martina McBride
* Aquarius/Let the Sunshine In – The Fifth Dimension
* Better Days – The Goo Goo Dolls
* Bridge Over Troubled Waters – Simon & Garfunkle
* Calling All Angels – Train
* Changes – David Bowie
* Dare You To Move – Switchfoot
* Don’t Dream It’s Over – Crowded House
* Don’t Stop – Fleetwood Mac
* Dream Weaver – Gary Wright
* Drive – Incubus
* Everyday People – Sly & The Family Stone
* Flying Without Wings – Ruben Studdard
* From a Distance – Bette Midler
* Go the Distance – Michael Bolton
* Greatest Love of All – Whitney Houston
* Hands – Jewel
* Heaven Help Us All – Stevie Wonder
* Hero – Chad Kroeger featuring Josey Scott
* Higher – Creed
* Holding Out for a Hero – Bonnie Tyler
* I Am Changing – Jennifer Hudson
* I Believe I Can Fly – R. Kelly
* I Can See Clearly Now – Jimmy Cliff
* I Hope You Dance – Lee Ann Womack
* I Turn To You – Christina Aguilera
* I Will Survive – Gloria Gaynor
* I’ll Be There – Jackson 5
* If You Believe – The Wiz Original Broadway Cast
* I’ll Stand By You – The Pretenders
* I’m Coming Out – Diana Ross
* It’s My Life – Bon Jovi
* I’ve Had The Time Of My Life – Bill Medley & Jennifer Warnes
* Lifted – Lighthouse Family
* Live Like We’re Dying – Kris Allen
* Live Like You Were Dying – Tim McGraw
* Livin’ on a Prayer – Bon Jovi
* Living in America – James Brown
* Lovely Day – Bill Withers
* My Heart Will Go On – Celine Dion
* My Wish – Rascal Flatts
* Only Hope
* Over the Rainbow – Judy Garland
* People Get Ready – The Impressions
* Rainbow – Sugar Ray
* Reach Out and Touch (Somebody’s Hand) – Diana Ross
* Reflection – Christina Aguilera
* Return to Innocence – Enigma
* The River of Dreams – Billy Joel
* Show Me What I’m Looking For – Carolina Liar
* So Small – Carrie Underwood
* Stronger – Mary J. Blige
* That’s The Way God Planned It – Billy Preston
* That’s What Friends Are For – Dionne Warwick, Elton John, Gladys Knight
* The Boxer – Simon & Garfunkle
* The Impossible Dream – Frank Sinatra
* The Prayer – Andrea Bocelli & Celine Dion
* The Time of My Life – David Cook
* The Is My Now – Jordin Sparks
* Up Where We Belong – Joe Cocker and Jennifer Warnes
* Walking on Sunshine – Katrina & The Waves
* We Are the Champions – Queen
* What a Wonderful World – Louis Armstong
* What the World Needs Now is Love – Jackie DeShannon
* When you Believe – Mariah Carey
* Wind Beneath My Wings – Bette Midler
* World – Five for Fighting
* You Light Up My Life – Debby Boone
* You Raise Me Up – Josh Groban
* You’ll Never Walk Alone – Barbara Streisand
* You’re My Best Friend – Queen
* You’re the Inspiration – Chicago
* You’ve Got a Friend – Carole King
If you guys want to do to the same that would be great, people need to hear the beautiful words of songs like "On the Line", "We've Had Enough", "Heal The World" and soooooooo many more!! 
