I seen the Forza movie. As a small note, the opening music is at a low volume level, and you can somewhat hear it in the video. Anyhow, the video has some elements it has over GT4. The first is the popular European exotics (you know what I'm talking about), several other types of racing, (I think) 8 cars to a track as opposed to GT4's 6, customization of cars all the way down to car painting, and a race groupie stroking a car. It wasn't like a completely exciting introduction, but it does show some elements GT4 doesn't. Something else I noticed was visible drivers.
Regardless, the intro was pretty good. I'm now actually learning more about this game than in the past.