In RPGs like these, I actually tend to like it if the main protagonists voice actor/actress is fairly... neutral in his/her expression of emotion. The more neutral the voice acting is, the less restricted I feel with my choices. If my character totally sounds like some happy and friendly nice-guy then I would never ever make him do evil stuff because it would be out of character... And I'm the one who's supposed to create this character, right!? Nothing is supposed to feel out of character by default.
Just look at Geralt from The Witcher. I [censored] love Geralt. He is the perfect RPG protagonist, if you ask me. Morally and emotionally neutral 99,9% of the time. No choice is wrong or right. His voice actor actually acts as though Geralt has no emotions - which he hasn't according to Witcher lore! Makes most choices a lot more interesting. Even though Geralt is not a character I've created, I still feel like I can shape his story and character ark any way I want. Fallout is different, but the same principles should still be relevant.
I like Male Shepard for the same reason. If you're going to give your RPG protagonist a voice, make him sound neutral! However, that makes it even more important to give all the other characters around you a good and interesting voices. Define them. Give them emotions, morals, principles and such.