Captain Marvel did outsell Superman, for a time.
You could argue that he’s one of only 4 superheroes to ever claim the spot as being the genre’s No. 1 character.
Superman
Captain Marvel
Batman
Spider-Man
Whiz #2 has, by far, the fewest copies on the CGC census amongst the Top-7 books in the hobby (just my opinion: Action #1, Tec #27, Marvel #1, Superman #1, Batman #1, Cap #1 and Whiz #1).
If we were comparing a Whiz #2 (#1) in 9.4 to the recent Marvel #1 and Cap #1 9.4 copies—I think it would be a discussion.