I adore Angel. I was kinda "meh" on him before AtS, but once he got his own show he became a much more interesting and engaging character. He was OK on Buffy, but he kinda just had two settings, "Brood" and "Brood over Buffy". On AtS he had "Brood" and "Awesome" and "Funny" and "Dark" and "Singing" and "Philosphical" and "Dorky" and so much more... he was just a more fun character to see. I think that's the main reason why I love Cangel and dislike Bangel, but that's another argument.
I love Angel because despite his darkness and angstiness, he's still everything a hero should be. He's a true champion. I love his speeches to Kate ("If nothing we do matters, then all that matters is what we do.") and Connor ("Nothing in the world is the way it ought to be. It's harsh, and cruel. But that's why there's us. Champions. It doesn't matter where we come from, what we've done or suffered, or even if we make a difference. We live as though the world were as it should be, to show it what it can be.") Despite everything, he still fights the good fight, and I respect that. He's now my joint-favourite character with Faith.