My thoughts on Stan Lee:
He taught kids to read, to use their imagination, and what heroism is.
He taught kids the word "excelsior".
His most famous line: "with great power comes great responsibility" not only sums up the superhero ideal, and will likely be included in books dedicated to famous quotes.
He took a medium that was for kids and brought realism to it. With this he created (co-created) characters with flaws/weaknesses and put them in a real setting, his hometown--New York City. With this he respected his audience.
He gave America a mythology built around heroism...what you can do for your country (to abridge JFK's famous quote).
He became the face of comics in a way that was beneficial to Marvel, and the industry, however this brought friction with his industry peers.
At 77 years young, he started a new career as an actor, having made 40+ cameos in films, over an 18 year period, and became the most successful actor in the world.
He lived to see his creations enjoy the fame they never enjoyed during the 60s as the industry was devalued by society at large. Nowadays, it is the opposite, people all over the world, Africa, China, Korea, India, know who he is, and his creations, and those who followed his example at Marvel.
Stan "the Man" Lee lived a marvellous life. He is one in a Marvel.