(This is not to discourage anyone from reading or commenting if they disagree, just to give people a sense of where I'm coming from and what to expect.)
Speaking of pedestals...
Something that Buffy Summers and Jack Harkness have in common is that they are surrounded by people who tell them they are wonderful no matter what they do.
The difference is how they handle this.
Jack deliberately encourages people to put him on a pedestal. Buffy is much more uncomfortable with it, and more likely to discourage it. Take the contrast of Crush and Cyberwoman. In Cyberwoman, Jack put a gun to Ianto Jones’ head and told him to kill his dangerous girlfriend in order to prove his loyalty. In Crush, when Spike offered to kill his dangerous ex-girlfriend in order to prove his love, Buffy was unimpressed. When Ianto died, Jack begged the 4-5-6 to save Ianto, even at the price of many children. As Ianto died, Jack begged Ianto not to leave him. When Spike died, Buffy tried to convince him to not sacrifice himself not because of her, but because of his own worth. (“you’ve done enough!”) Jack cannot tell Ianto that he loves him, no matter how much Ianto may want to hear it. Buffy can and does tell Spike (even if Spike can’t accept it). Jack just wants someone in his life to be close to and tell him how wonderful he is. Buffy wants what is best for Spike.
Buffy pushes Spike away in late S6 partly because she knows that he will encourage her to do bad things, even things that will hurt him, and continue to tell her that she is wonderful. Jack fires Owen simply because Owen dared to question him (not because of Owen’s chronic unprofessional behavior). The one period I would say that Buffy encourages Spike’s enabling is in sort of late-mid S7, maybe from “Get It Done” onward. Buffy is very anxious about her ability to lead to the girls (rightly so) and increasingly relies on Spike’s unconditional loyalty. One rather telling moment is in “Storyteller”, when Buffy is arguing with the Scoobies about whether or not Andrew should be allowed to film them all. “Come on, someone has to agree with me,” she says. “Spike?” Since he currently is more then welcome in her life, though, Spike doesn’t automatically take her side in Scoobuments the way he does when the two of them are on the outs, such as in “Once More With Feeling” and “Beneath You”.
Of course, by not revealing first her relationship with Spike, and then her abusive behavior toward Spike to the other Scoobies, Buffy does encourage them to put her on a pedestal. But it’s still not quite the same level as, say, Jack Harkness failing to mention that he once gave children to aliens. That said, Jack does eventually reveal what he did, when they need to know. And it's interesting that the person who knows the most about Buffy’s worst behavior, Spike, is also the one who puts her on the highest pedestal.
There’s also a difference of lifespan between Buffy and Jack. Jack has lived a long time and will live a much longer time. He has to constantly reinvent himself. Buffy, by contrast, expects to live a short, brutal life. If she lived forever, she might find less reason to be honorable. If Buffy hadn't already expected that Dawn would outlive her, she might have been more willing to sacrifice her in “The Gift”. Likewise, if Jack expected Steven and Alice to outlive him, he might not have given them up for the greater good. (Which also goes to show that the honorable thing to do isn't necessarily the best thing to do.)
Then again, honor was never Jack Harkness’ thing, that I can recall. He was, after all, a con man, albeit one with a heart of gold. So how much of this is personality, and how much is situation? I don’t know.
One more thing: Both Buffy and Jack have their followers turn against them. Buffy is thrown out of her house in “Empty Places”. Jack is betrayed and *killed* in “End of Days”. Both times, they are proven to be right, and their followers screw up without them. Both times, the betrayal happened in part *because* their followers put them on such a pedestal. Jack and Buffy should be able to fix anything. If people are dying and they aren’t stopping it, no one wants to listen to them anymore.
But here’s the difference: Jack takes his power back with hugs and forgiveness. I once heard someone criticize Buffy by saying that although she forgives both Spike and Faith, she undoubtedly sees it as *her* forgiving *them*, and does not acknowledge her own bad behavior toward them. I…frankly don’t buy it (although Buffy certainly owes them both apologies they will never hear, just as she will never let them give her the apologies they owe her), but I might well buy it for Jack Harkness. On the other hand, his team did kill him, and they almost destroyed the world, so arguably he had the right to perceive himself as the one offering forgiveness, not receiving it.
Buffy also returns to the fold after a crisis. She offers no forgiveness, and asks for none. When the potentials try to claim that the explosion that killed some of their number was punishment for them choosing Faith over Buffy, she tells them it was not. “That could've just as easily happened to me.” When asked if she’s back, she says, “I guess I'm not leaving.” Faith continues to sleep in Buffy’s room. This is because Faith is injured, but there is also definitely something symbolic going on here. Buffy’s back, but things will be different.
Jack, on the other hand, leaves without warning at the end of episode where he returns. Things will be different, all right, but simply because he is putting his personal wellbeing before the welfare of earth. If Buffy has a superiority complex because she’s the slayer, Jack really thinks his personal problems are more important than everyone else’s, because he has to live with them forever.