You are charged with making a presentation for alien visitors about a great thing that humans have accomplished. What would you show them?

You don't need to accomplish anything in particular with your presentation just show something you sincerely feel represents humanity and represents us well. Sincerity matters most.

Further, you don't need to try to represent all of humanity. People all over the world will have the same chance. You just need to show the part you care and know about best.