First person 360 degree (or maybe just 180) movie would be awesome. On a fixed track as the movie plays, but you can move your head around, see the sights a bit, look at the action you want to see. Or maybe in practice it wouldn't be so cool.
What about the character voice? What do you think is more engrossing, a silent protagonist that we live through or one we see through but can also hear speaking?
I grew up on the silent protagonist, it seems easier for me to become engrossed in something when I feel like people are talking to me and the response is whatever blanks my brain happens to fill in, rather than listening to someone else say words "for me" as it were. I know there's a lot of people that disagree and want to see the end of the silent protagonist in games, so I can imagine it not working out well in a movie at all.