I just want to add one more thing about MP4... (Oh! Metroid Prime 4 shortens to "mp4?" Huh...)
I turned off the human voices, and it's a good change to a problem that many have cited.
At first, I had voices set to 50% volume, which worked very well for the first mission where soldiers are barking or talking to you; and it worked so well, because it gave me the impression that Samus barely cares what people are saying. She listens and then keeps focussed on her own thing.
When the first stranded scientist/marine is introduced in a cutscene, it was good to hear his monologue, introducing the character a bit. But then I decided to turn voice volume down to zero. This had an interesting effect on further cutscenes: they play out like mimes. I mean, you can just see him in his suit making gestures, and Samus occasionally responding with an action of her own. The techno-babble is lost... And I don't have subtitles turned on... But this is totally okay with me.
Just wanted to share that, in case it sparks some thoughts ^_^