Just let it go OP. Venting is normal and healthy, but if you are jealous which you say you are, you need to focus on getting rid of that - jealously is such baggage - you don't need it!
The examples you posted do sound extreme. My parents are helping build our kids' college funds, which I think is awesome and we wouldn't be able to do it on our own. We both work, and work hard, and we otherwise live a pretty modest lifestyle. Small, old house, one car, and the only vacations we take are to stay with family. I feel very lucky that my parents are able to help a bit with college funding, which we couldn't afford to save for if we also wanted to have any emergency savings and some retirement. The way they see it, they are retired, have money, and this is partly how they want to spend it.
That said, in my hometown, many of my friends live in near million dollar homes their parents bought them - their starter home. I also don't get it, but it's not my life and I wouldn't say I'm jealous. On the contrary I'm proud I got away and making it my own in the DC area.