I was never a big player of D&D. By the time I lived somewhere I could find a regular game other systems had come out and I rapidly narrowed my focus to I.C.E.;s Rolemaster system. However, without D&D it's very likely Rolemaster would never have existed.
If Rolemaster didn't exist then I wouldn't have become part of a gaming group where I made some of the best friends I've ever had. I would never have created the character of Ranuel and been inspired to write stories about her adventures. I may not have discovered the now gone About Roleplaying games forum which lead to me finding ULF where I found people who have become family. By taking tabletop war gaming and transforming it into something entirely new Gary Gygax changed my life significantly.
And it changed the life of just about every American geek under 50. Gaming gave us a focus to build lasting social networks that comics and speculative fiction could not. The average fen might make it to a convention once a year or less. . The average gamer meets with his or her gaming group about once a week. It taught life skills like cooperation, negotiation, advance planning, and thinking outside the box that corporate motivational trainers charge hundreds of dollars a head to lecture about. Unless you were the GM you could start playing most games with a pencil and some borrowed dice.
Thank you Gary for all that you inspired.