There's not much "stuff" I miss. Sure I had some heirlooms I lost that would have been nice to still have. Pictures and antique furniture and a few good guns (like a 16 gage Winchester Model 12 and a late 40s 4" S&W Model 10). But I can replace most of that if I had the serious desire to.
I think the biggest thing I miss from my youth is the big empty field at the end of my neighborhood. All the parents on weekends and summer days would kick us all out of our houses to go play. That field was our sportsball field (mostly Calvinball), hide and seek place, tag field, and general meeting place. I haven't yet found something so convenient and central for meeting up with peers. Nor the sense of freedom and independence we had in that field.