He is just making money, but yeah if that is all you are after (hopefully kids aren't), then he is definitely more successful. His parents may face several charges though because technically it is advertising to children.

There is a person in Korea who is making a lot of money doing something similar to Ryan Kaji (reviewing toys and playing on youtube). Apparently, her parents are strongly encouraging her to make a lot of videos and psychologists who've spoken with her or have seen a lot of her videos express concern.

I don't think Greta faces similar risks because she is much older and has a very different goal.