They're my favorite Slytherins; I like them because they are obviously stronger than the other Slytherins emotion wise. I'm sure they are pressured into the Dark Arts, but those few don't give in. Remember: Being a Slytherin does NOT mean you are evil, it means you are cunning, but most times the cunning are the evil. However Regulus, Snape, Andromeda, etc show that that is not always the truth.
sometimes its good to defy the odds. If you dont the stigma grows stronger and stronger and more stereotypes are made. Look at Peter Pettigrew a Gryffendor gone BAD. Things arent always what they appear to be...Snape played his part well though, he did keep us guessing through the whole series.
Don't get me wrong, I love Draco to bits, but I wouldn't really consider him good, even by slytherin standards. He's bullied, taunted and been down right evil at times. Yes, he didn't wan't to kill dumbledore, but that's merely due to the fact he didn't want him or his family killed. Even after Harry saved him, he still went crawling back to the deatheaters.
Maybe he changed over the nineteen years, but that's not concrete.
Severus is my all-time favorite. Everything has already been said about him : bravery, cunning, intellectual brilliance, wit, loyalty, devotion (and let's put it like this, Alan Rickman's voice and physique, but that's just me).
But I was touched by Regulus and his kindness to Kreacher. And Horace Slughorn is just the kind of fellow you wish to have a drink with. He has good tastes and enjoys good food and good company and conversation.
I am less sure about Draco. But I will give him the benefit of the doubt as he was young and under the influence of his relatives, and enduring a lot of pressure from them while having qualms about his family's involvement with Voldemort. He could change later. I like to think he had renounced his prejudices. I hope so. I also like a 'good' Draco.