It sometimes depends on the situation that you are describing. Here are some examples For example: In school: He is the top of his class. State of happiness: He is on top of the world. / She is on cloud 9. (slang) At a job: He is high up in the company. / I am at the height of my career. In general: She is number 1! I hope this helps!

No, DO NOT say you stand on top of people! You can say, that you 'stand head and shoulders above others', however this would be extremely boastful. This is more something that others might say about someone who is outstanding in their field. In relation to countries, you might say that a particular country is a world leader in ..whatever it is you are talking about.

To my knowledge, "to stand on top of people" doesn't exist. "To be on top of the world" has a different meaning; it means to feel very happy or to feel wonderful/great. If you would like to say someone is outstanding, you can just say "he is outstanding". This already implies that he stands out amongst people because of being a certain way or having a certain ability. You can also say something like "he stands out from the crowd with his superb computer skills" :)