Well, a lot of artist's "best" albums came AFTER their debut, but here's some debuts that stand out for me...
The Rolling Stones--ENGLAND'S NEWEST HITMAKERS
Frank Zappa/Mothers of Invention--FREAK OUT!
Led Zeppelin--LED ZEPPELIN I
Jimi Hendrix Experience--ARE YOU EXPERIENCED?
Elvis Costello--MY AIM IS TRUE
Talking Heads--TALKING HEADS 77
The Doors--(self-titled)
Motley Crue--TOO FAST FOR LOVE
Black Oak Arkansas--(self-titled)
Lynyrd Skynyrd--PRONOUNCED LEH-NERD SKIN-ERD
Son Seals--THE SON SEALS BLUES BAND
Hound Dog Taylor & The Houserockers--(self-titled)
Randy Newman--(self-titled)
Harry Nilsson--PANDEMONIUM SHADOW SHOW
AC/DC--HIGH VOLTAGE
Miles Davis--BIRTH OF THE COOL (his first as a LEADER, I think...)
The Vince Guaraldi Trio--(self-titled)
Tiny Tim--GOD BLESS TINY TIM
The Stooges--(self-titled)
Blood, Sweat & Tears--CHILD IS FATHER OF THE MAN
Chicago--CHICAGO TRANSIT AUTHORITY
Guns 'N Roses--APPETITE FOR DESTRUCTION (of course)
John Lennon--JOHN LENNON/PLASTIC ONO BAND