I'm hard pressed to come up with just one. I'm 75 and so much has changed in my lifetime. Yep, I remember when my grandparents got indoor plumbing. I certainly was grateful for that!!
I was always smitten with the stars when I was a kid and I think that most of the coming generations will not be able to experience the pure magic and awe of looking at the night sky and seeing the milky way in all its glory. There just aren't many places left in the world where you can do that. You might find this an interesting site on the subject.
http://www.darkskiesawareness.org/idsc.php