Humans compare things all the time. If the comparison turns out in our favour we feel good, if it doesn’t we need to do something to explain it away. One of the most popular ways of explaining other people’s success away is by
looking at what they have and we don’t: talent, rich parents or simply being at the right place at the right time. In the short run you will feel better when you do this because it assures you that you don’t need to change anything.
In the long run this behaviour is hurting you: not only do you insult the other person’s hard work and dedication by explaining it away (even if you don’t say a word), you actually put yourself down by indirectly saying ‘I couldn’t do this because I don’t have the talent, the rich parents or it’s the wrong time to start’.
Talent is not enough. Money is not enough (broken celebrity kids?) and while it can help being at the right place at the right moment lots of others were there too and didn’t become successful. Give other people the credit they deserve by recognizing their hard work. And if that person’s success makes you jealous look at it as an opportunity to ask them the secret of their success.