The characters with definitive runs are:
Spider-Man - Lee/Ditko/Romita
Fantastic Four - Lee/Kirby
X-Men - Claremont
Thor - Simonson
Captain America - Brubaker
Hawkeye - Fraction
Black Panther - Priest
Punisher - Ennis
Wolverine - Hama
Daredevil - Miller
Hulk - David
Guardians of the Galaxy - DNA
Characters where it's debatable:
Iron Man - A lot would say Michelinie/Layton but Fraction is also a contender.
Avengers - Busiek, Stern, Thomas, and Hickman are all contenders. Maybe even Bendis.
Dr. Strange - Lee/Ditko or Englehart.
Deadpool - Kelley or Duggan
Ms. Marvel (Carol) - Not sure tbh. I guess it's between Brian Reed and Kelley Thompson?
Doug Moench/Paul Gulacy: Shang Chi: Master of Kung Fu. One of the best drawn best written runs you'll find.
John Byrne- She-Hulk
Frank Miller- Daredevil
“Somewhere, in our darkest night, we made up the story of a man who will never let us down.”
- Grant Morrison on Superman
Claremont and Byrne on UXM
Brubaker and Epting on Captain America
Miller on Daredevil
Nocenti and JRJR on Daredevil
Brubaker and Lark on Daredevil
Ellis and Deodato on Thunderbolts
Ennis and Parlov on Punisher MAX
Conway and Andru/Mooney on ASM
Aaron and Boschi on Ghost Rider
Fraction/Brubaker and Aja on Iron Fist
"Who wouldn't go out with the Black Widow? I'd strangle a litter of kittens for one dinner with her!"
Adrian Toomes aka the Vulture
"Natasha Romanoff, A.K.A. Black Widow - ex-KGB, formerly with S.H.I.E.L.D...Probably the brains of this operation.I have followed her career, and she has been consistently UNDERRATED."