I'm somewhere in the middle of Uncharted 3, leading Drake on a ridiculous adventure upon which he's more than happy to be a part of, and it occurred to me: Unlike every other character in every other game I've ever played ever, I was 100% empathetic with Nate. We weren't just on the same page, we were on the same word.
This entire chase, front to back, is a joy to play.
When I talk about empathy I'm not talking about technical synchronization, like the translation between controls and movement (although Drake does have an eerily natural way of moving around). What I'm talking about is Nathan's emotional state; his attitude.
The dude enjoys risking his life. Ultimately, it isn't for the treasure or moral obligation. He's just having fun, and the closer he gets to dying horribly, the more intense the situation, the better.
On my end, as the player, I enjoy risking Drake's life, and it isn't for treasure or morality for me, either. Jumping off a cliff and madly grasping for a hanging rope, or being chased by a bunch of guys with assault rifles through the collapsing halls of some ancient temple; that's a lot of fun. And if I die, I'll just come back a few seconds earlier as if nothing happened, so I don't give much of a shit if I get gut-shot or slip and fall down a mountain. I act as if consequences don't exist, just like Drake.
And Drake, despite the quips and sunny personality, is completely homicidal. He has no reservations about killing another man, or men, or whatever. And Nathan doesn't limit his killing sprees to a few impersonal shots from a sniper rifle. This guy will sneak up on a dude, snap his neck, and then make a joke out of it, "Oh, that's your neck!", which makes me smile, because I didn't give a shit about that dude's life, either. I'm playing a video game, challenging the mechanics put in front of me, not the morality.
What helps to cement this sense of empathy is the contrast between Drake and all the other characters, who often ask Nathan, "What the fuck is wrong with you?"
And Nathan doesn't really have an answer to that question, because it's hard to explain to someone that you're treating your own life as if it were a video game.