Slang

In class, we're currently trying our best to incorporate old slangs of the 20s to the 80s into our little skits.
So I was wondering--
During our little research of slangs, I realized that we still use a lot of phrases from 20, 80 years ago. For example, the word "crush" (as in I have a crush on someone) was around ever since the 1920s. We discussed this in class a little bit, but what is it about some slangs that are still relevant today? What are some new slangs of our generation, and which of those do you think will last and still be used by the upcoming generations? Please justify your answer.

Jeewon K.