Multiplayer makes sense, I hadn't thought of that. And for some games I can see making your own soundtrack in single (I always do in racing/sports games, and I can def see doing it in a game like Bulletstorm), but for a game like Dead Space that's all about atmosphere I feel like changing the audio environment would ruin the experience.
That's interesting to me. I don't mind silent characters, because I am the character (even if it's 3rd person), and I'm not a non-entity to myself. If anything, having a talking protagonist (when I don't get control over the dialog) makes it harder for me to get into the game, because then they're not me and I have a harder time empathizing (not a hard time, mind, I'm not a heartless monster, I can empathize with people just fine, but it's easier to empathize with myself). Plus if the protagonist talks it opens the door to him saying stupid things that break my immersion.
That makes me think of a time in Dead Space 1 where Hammond is saying something about the Security Wing, but because of his accent it sounds like "Security Wang", which made me laugh and completely destroyed the tenseness that had been built up to that point. Dead Space's atmosphere is quite good though, so I quickly got back to being tense.