Good darn question. In no particular order:
Paul McCartney
John Lennon
Freddie Mercury
Roger Daltrey
Paul Rogers
Except for the first two, this list will change in one hour.
In the FWIW category I saw a chart once comparing Freddie Mercury’s highest sung note (not a scream, but a sung note) and Paul McCartney’s. Both covered FOUR FULL OCTAVES and Freddie won by a half step. The average person has between 1.5 and 2 octaves.