Keifer's a good actor, but his lines in MGSV really aren't worth his talent, I found him to be mostly nondescript, bringing nothing to the role that any number of other voice actors couldn't have accomplished. His acting is fine, but his dialogue he is given to perform extremely underwhelming.
The tapes are where the bulk of the dialogue was, and even they weren't that interesting, his lines within the game are bare bones at best. I suppose that's more a knock against the writing than the voice acting, but I didn't hear anything from Sutherland that made me think, "man it was a really good idea to get someone like him to voice act the protagonist for this game". Big boss himself didn't really come off as badass to me, just kind of an empty cipher, his is not the performance I will remember thinking about that game a year from now. I was way more interested in hearing Miller, Ocelot, and Code Talker having conversations with each other than I was listening to Keifer just kind of drawl his way through conversations to prompt the more interesting characters to say their lines.
In the end, Keifer adds a more down trodden weary quality that I don't think David Hayter could have pulled off with his usual Snake voice, but the dialogue makes me feel like they wasted the actor's talent, sort of like Dinklage in Destiny, it feels like they wasted the talent and potential they could have had by giving the actor nothing interesting to say. Unlike Destiny, at least in MGSV the other characters managed to at least somewhat make up for that, until the plot dives off a cliff in chapter 2.
