I find it best to listen to a variety of music that is well recorded, well listened favorites. I burned a CD that I used (and continue to use) for auditions. Some show soundstaging, others impact, etc.

I left out classical even though I own a number of pieces but don't listen as often as I used to...

Shirley Horn - The Music That Makes Me Dance
Rebecca Pidgeon - Spanish Harlem
Michael Franks - Dragonfly Summer
Dianne Reeves - Never Too Far
Fourplay - 101 Eastbound
Steely Dan - Jack of Speed
Grace Jones- Don't Cry - It's Only The Rhythm
Larry Carlton & Lee Ritenour - Take That
Herbie Hancock - Butterfly
Lee Ritenour - Boss City
Dave Brubeck - Take Five
Miles Davis - So What
Buddy Guy - Sweet Black Angel (Black Angel Blues)
Cassandra Wilson - A Little Warm Death
Troubles What you’re in - -Fink (Live from Union chapel London)
Keith Dont Go - Nils Lofgren
Daggers & Knives - Woodes
Hey Now - London Grammar
Caught our in the rain (live royal Albert hall ) - Beth Hart
Mountain Time (Live at Carnegie Hall) - Joe Bonamassa
Serious - Bernard Allison
River Child (acoustic ) - Civil Twilight 
Heaven I know - Gordi 
Parade of the dead (unplugged) - Black Label Society
Blessings & Curses - Wolves at the gate
Euphoria - Stalgia
Mindlessness - Jimmy Wahlsteen

Lots of different types of music to hear - full soundstage, crisp vocals, a punch is bass, the feeling like the artists are actually in the room with you. If these don’t sound great on your system you need to replace it. Lol 

I don't know if my favorite music is appropriate for another person to test speaker performance with since what we like is all personal taste.
My approach is to bring my favorite music (both poorly recorded and well recorded).
But I have 3 albums I use for testing Dire Straits Brothers in Arms, Bella Flec Flight of the Cosmic Hippo, and Jeff Beck Wired.
If a speaker system can satisfy me with these albums I am good to go.
Some great suggestions here, thanks.

However, with one or two exceptions, there's very little here in the way of excellently recorded orchestral music, which I think presents a unique test for loudspeakers.  Mercury Living Presence has some good stuff but the application of modern recording techniques has raised the bar substantially.  

Any recommendations in this genre would be appreciated.