True dat, what would be the real purpose of keeping you alive? Did he want to gloat in your face particularly as he pried out the Eyes of the Falmer? Did he want to see if he could really thwart a Daedric Prince? Was he testing Nocturnal or Karliah or you? All of those sound pretty dumb to me.
To be fair, Kodlak spent his twilight years trying to evade Hircine, yet death came before that happened. Given that it was the Silver Hand who slain him, I can't help but think Hircine had a hand in that. I know Werewolves are his creatures, but he does love it when a chase it turned inside-out, as "Ill Met by Moonlight" taught us. :)
TL;DR: It's not like the others were any smarter.
For me, I'd second Kodlak Whitemane. Certainly the most honourable leader; he cares the most for his people, too, whereas the others barely acknowledged the existence of theirs. I suppose it's kind of ironic; the one leader who doesn't call himself a leader is the guy who acts the most like one.
I've had quite a bit of time to think about this, and even then my answer is a bit odd. The person I would save isn't exactly a guild leader, though people do follow him.
Miraak. I wanted nothing more than to be able to team up with this bastard. His knowledge of Dragon Shouts are useless if he dies!
Because I have done the questline so much, yeah, another vote for Kodlak here. I STILL get a bit misty in the eyes when I read his journal, though not so much when the protagonist was named Mr. Buttons. There's a noble sadness to the Old Man that kinda tugs at the heart strings. The way he just kinda sits in his chair waiting for you to kill the Glenmoril Witches. ARGH!! *sniff, sniff*
I've only done the TG once or twice, but I hate the last half too. Would have been totally fun to stick it to Nocturnal and join up with Mercer.
So I think, overall, we've all established that the best guild buddy we'd all save (dictating on the number of people choosing this person) would finally be... Kodlak Whitemane.
He's strong, reliable, and knows how to hold his own. But, obviously, numbers can overwhelm. All he wanted was to drink in the swimming pools of Sovngarde mead and he couldn't even achieve this without the help of his fellow mates. If I were given the choice, I'd sacrifice myself in a heartbeat if it involved this old man. I'd raise my shield in his honor and stand back-facing-back so that this world might never overtake us.