Metal Gear Solid 4 gets my vote for two reasons.
One – The voice acting is simply great. Kris Zimmerman directs the voice actors and, though she has a great cast, she’s definitely doing something right. I know most of the cast consists of mainstays to the series (David Hayter, Debi Mae West, Jennifer Hale, etc…), but even the newcomers are dead on with line delivery. I’m always blown away by the voice acting in the Metal Gear games.
Two – The voice actors consistently deliver great performances no matter how hammed up or ridiculous the script is. It’s no surprise that the story of the Metal Gear series consists of many outrageous twists and turns. Clones, giant robots, ninjas and life-altering nanomachines just scratch the surface of the story. Throughout all of this ridiculousness, the actors remain solid.
Out of all the video games I’ve ever played, only a few have made me want to rewatch some cutscenes multiple times just for pleasure of watching them. Metal Gear Solid 4 is one of them.