If we're going by one role, then David Kaye should win.
I don't know how that's possible. I play as male Shep all the time and he's quite capable of inflection while femShep constantly sounded bored with everything she said, which made her boring herself.
Mark Meer has really one tone. Hale will actually more her voice up and down octaves necessary to show different emotions. When she needs to threaten, she sounds threatening. When she's trying to comfort someone, it sounds like she's comforting someone.
The best way to put it might be this:
Mark Meer might actually sound like a soldier.
Jennifer Hale sounds like a human being.
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TheRock ~ Slow dramatic zoom-pan. Doesn't phase the hooded man.