Both actually! I consider these books to be iconic because they are very popular or are critically acclaimed or appear on many challenges, often fulfilling 2 or 3 of the above. However my primary purpose in creating this challenge was to make a list of book icons that I can use to more rapidly assemble future challenges (frequent publishers should understand).
I am quite sure you will enjoy this challenge, with a good chance of scoring well no matter what fiction genres you prefer (only children's picture books were omitted). I think it makes a decent mid-size life-time TBR, if continually supplemented with newly published 'classics'.
BTW, I deliberately repeated "The Stranger" & "The Outsider". Possible free point! The repetition of Dorian Gray is accidental (I failed to eliminate the icon with incorrect spelling).