Not sure I can do a ranking off-hand, but some food for thought. These are albums:
In the Wee Small Hours - Frank Sinatra
Ella in Berlin - Ella Fitzgerald
Nina Simone’s Finest Hour - Nina Simone
The Astrud Gilberto Album (or the original Getz/Gilberto album) - Astrud Gilberto
Ella and Louis - Ella Fitzgerald and Louis Armstrong
Ella and Louis: Porgy and Bess - Ella Fitzgerald and Louis Armstrong
Tony Bennett at Carnegie Hall - Tony Bennett
We are in Love - Harry Connick, Jr.
The Tony Bennett/Bill Evans Album & Together Again - Tony Bennett
The Cole Porter Songbook - Ella Fitzgerald
Blue Bossa - Ana Caram
Come Away with Me - Norah Jones
At Mister Kelly’s - Sarah Vaughan
Dinah Jams - Dinah Washington
Anita Sings the Most - Anita O’Day
Francis Albert Sinatra and Antonio Carlos Jobim - Frank Sinatra
Lady in Satin - Billie Holiday
Lady Sings the Blues - Billie Holiday
Chet Baker Sings - Chet Baker
Songs for Swingin’ Lovers - Frank Sinatra
Hell, anything else by Ella or Nina or Billie! We should do a list of the best tracks by those three!