I am going to commit the comic book equivalent of sacrilege and admit that I find Stan Lee almost unreadable. No one needs to be reminded of all the characters Lee co-created and the massive impact they have had on popular culture. Having acknowledged that, I need to point out that Lee wrote some of the clunkiest dialogue in comics.
Here is an example from Doctor Strange's enemy the Dread Dormammu. "When last we fought, I pledged my word to attack Dr. Strange no more!! But I am not so doing! It is Mordo who attacks him -- Mordo, using the power of Dormammu! The power that I give him! Then, once Strange is destroyed, there will be none remaining who can stop my conquest of Earth, the home of the human race!"
In Stan Lee's defense, this was written to be read in a serialized format and any given issue might be some reader's first introduction to the ongoing story. There must be a less intrusive way to catch new readers up than having characters shout their names and motivations at the reader. I suspect even an audience of eight year old boys would know that Earth is the home of the human race, as opposed to Humanland or something.
The art of Steve Ditko is a bit of an acquired taste, but it is amazing in its detail, particularly in the detail he puts into the faces of even minor characters. His extra-dimensional backgrounds are as abstract as anything by Dali or Escher. He sticks to rigidly square page layouts with the formality of a haiku poet, and like a poet he reveals that formal structure can be creatively liberating.
I am deducting one star for Lee's dialogue and another star for his formulaic repetitive plots. That leaves 3 stars for Ditko's art, and for that of his successor on the book Marie Severin and Dan Adkins.