Doing speech about half-life 2 and valve, need suggestions??!?

i am doing a speech for my speech cl about valve and there games, like hl2, portal, tf 2 so on. i cant have any notes with me, unless they are contained in a visual aid, which is required, and has to be 5-7 minutes. any ideas how i should go about doing this, and making it interesting to those who don't play video games??? THX