Nolan North is a name so legendary in the world of videogames, there's a "Nolan North voice" option in Saints Row IV. But the roles he's probably most well-known for (even if you didn't know it was Nolan North) are Uncharted's Nathan Drake and the "SPAAAAACE!" core in Portal 2 (along with all of the corrupted cores, and the defective turrets). What else has he done?
Other than Nolan North, the big name in videogame main characters is Troy Baker. That's not to say they're the only ones in games, but - let's face it - Troy Baker was both Bioshock Infinite's Booker DeWitt AND The Last of Us' Joel. That's the two main characters of 2013's biggest games. And on top of all of that, Troy Baker has voiced:
Kevin Conroy is the best Batman, having started in the role in Batman: The Animated Series. On top of that, he's a bit of a weird choice for a voice actor, since he's actually a Julliard-trained actor, having been classmates with Kelsey Grammer, Christopher Reeve, and was even roommates with Robin Williams. So far, his voice career has including such memorable roles as: