Writing a good E3 speech is a surprisingly skilful pursuit - you have to make your game sound incredible, but you're usually early enough into development that actually saying anything meaningful would give too much away.
The middle ground, then, is to shoot out non-specific platitudes - things like "it will change the way you play", or "you've never seen a man's legs slough off like this". Lights go down, trailer comes up, perfect.
This quiz honours the best of Xbox's announcements over the years. The venues might have gotten bigger, and the content slightly less, er, racy (here's a clip that implies ex-head of Xbox, J. Allard had had intimate relations with model Jenny McCarthy (opens in new tab)), but the speeches are still a mix of non-statements and incredibly specific information that'd make your parents tut and say "what even is this?" The skill is in being able to decipher them. Give it a go.