I have seen a ton of vids for GW2, and of them, I think this series is the best when it comes to showing what GW2 will be like. IF you don't want to listen to all the initial commentary, then jump to the 5 minute mark of the first vid. After the first one, the 2nd and 3rd video's automatically change.
Anyway, this demonstrates the starting of the human race, and I think gives the best example of what it will be like to play GW2. It later moves into the Charr demo in the 3rd vid.