The stories and characters will live on a long time; humanizing superheroes (and villains) is not easy to do but Lee made it seem effortless and inspired generations of creators, and not just in the "comics" field.
But the morality he promoted was even more powerful. Taking strong, unapologetic stands against racism and bigotry was not an easy thing to do in the 1960s. And "With great power comes great responsibility" is legit one of the greatest, most concise moral edicts of the post WW2 era.
Incredible legacy from a guy who mostly just thought he was writing fun little stories for kids and teenagers. RIP.