Best debut album

As an R&B lover, I'd say:

Mary J. Blige -- What's the 411
Keith Sweat -- Make it Last Forever
Lauryn Hill (solo) -- The Miseducation of Lauryn Hill
Missy Elliott -- Supa Dupa Fly (I remember seeing this in a Record Store posted everywhere, and I thought "who is she and why should I but that CD?" until I got home and listened to it.  I'm glad I took that chance.. I've loved her ever since.
 
And on another note, I really loved:
Madonna -- Madonna  (I always thought HOLIDAY would be a classic)
Nora Jones -- Come Go with Me
English Beat -- I Just Can't Stop It (my most listened to CD in college)

Michael Schenker Group S/T
Hard Rock MASTERPIECE as far as the music. Production not so much😒
What a Shame.

+1 for Chicago Transit Authority

also Kansas’s debut album is their best work, IMO

Led Zeppelin (first album), for me as a teenager, for Classic Hard Rock.
Meet The Beetles, for me as a 9-year old, the music that began it all.

Air - Moon Safari
Brian Eno - Here Come the Warm Jets