"Discography
During Ella's 50-plus year career she recorded over 200 albums and around 2,000 songs. "

— so take your pick-
I epecially like her duets with Louie Armstrong

Http://www.ellafitzgerald.com/index.php?…

Ella's version of "Black Coffee" was released in 1949 on the album "Miss Ella Fitzgerald and Mr. Nelson Riddle Invite You to Listen and Relax."
Http://www.allmusic.com/cg/amg.dll?p=amg…

Sinatra's first version of "The Coffee Song" is a tougher question. It was released as a 78rpm single in the mid-1940s for Columbia Records (record albums/LPs weren't introduced until 1948). The first Sinatra album it appears on was "Ring-A-Ding-Ding!" in 1960 (Reprise label).

This is a difficult question to answer as Ella's most popular songs were different in every country. In the UK, her most popular songs were Every Time We Say Goodbye and Manhattan. When she started singing these songs in the UK she would get the lyrics wrong which astounded the audiences. This is because those songs were not popular in other countries so Ella had to start learning the lyrics for her appearances here in the UK.

As someone else on this page says, she is known for so many songs it is hard to say which is her most famous song. If pushed, I would probably say A Tisket A Tasket. This was certainly her first million selling recording. Co-written by Ella, it was the song that made her famous at the age of 21. It also set her up for the popularity that she maintained for the rest of her career.

Later on there were other songs that became popular because she always sang them in concerts. These include Mr Paganini, Lady Be Good, Summertime, Don't Be That Way, Mack The Knife, How High The Moon.