Lisp has jokingly been called “the most intelligent way to misuse a computer”. I think that description is a great compliment because it transmits the full flavor of liberation: it has assisted a number of our most gifted fellow humans in thinking previously impossible thoughts.
It is hard to speculate what the world would have looked like without them.
Certainly, people were doing exciting work at Xerox PARC in Paolo Alto but it was Steve Jobs who turned these ideas into a commercial success. And then he went on and did it again with other interesting but not quite polished ideas, such as selling music on the Internet, or tablet computers.
And John McCarthy, through Lisp, not only introduced automatic memory management, but allowed other smart people to think differently about programing and expressivity. Today’s many languages own much of their syntax to C (unfortunately), but most of them derive their power from ideas first dreamed in Lisp.
“Think different”, for them, was clearly more than just a slogan.
Unfortunately, it is the nature computer history that most of the giants are now reaching an age when obituaries are getting more likely, and another birthday party slightly less so.