This comment, which I found in the comments section of Stan Lee's obituary, in The Guardian conveys what I think better than I ever could:
Whatever the exact creative balance was between Stan Lee, Jack Kirby and Steve Ditko, there can be no argument that between them they created something of lasting cultural importance - and incomparably so. I'm ashamed to say that I only learned of Steve Ditko's own death after seeing an obituary panel at the foot of this article. A marvellous comic-book artist, with a beautifully elegant and fluid style - his cover for The Amazing Spiderman 33 ('The Final Chapter') is, in my humble opinion, one of the most visually striking and original images the medium has produced.
Bonus:
First appearances of Spidey and Thor... via The Naked City.
Featuring Batman's The Penguin