My partner and I were discussing this question. She feels that she grew up even more poor than I did, because I had a color tv growing up and she did not. And then we got to talking about how our kids probably have a different perspective on this question than we do, because they now have basically everything that she and I thought only rich people had.
So we asked the kids. Their first answer was "money", which is an answer I'm kind of proud of because we have previously discussed that we are rich because we have money, not because we have lots of fancy things. People who have lots of fancy things have spent all of their money and aren't rich anymore, they just have fancy things but no ability to buy anything. Being rich means you can buy whatever you want, not that you have whatever you want.
But upon further probing, they came up with a variety of more silly answers. In their view, the "rich" kids have brand name clothing (Gucci, Hollister, etc.) and get each new iphone when it comes out. Basically everything that I (and they) consider to be wasteful purchases, conspicuous consumption done for the sole purpose of showing off, akin to lighting hundred dollar bills on fire at recess. They have no concept of how truly rich people live, with servants and private aircraft, and I think I prefer to keep it that way.