Snape ended up being the one who was set up as the "bad person doing good things" guy
I always liked that guy. Sure he hated Mr. Potter, though at the time I thought he was was mostly against celebritism in general which I support, but he was fair and strict and always had his ambitions squashed. Heck him disliking Mr. Potter, someone who has everything given to him including the love and adolation of his peers, when he himself takes everything seriously and works hard and yet is still not rewarded for it makes sense as well.
-Yeah lets just say I actually found the "excuses" the books introduce to be worse then leaving it open. They didn't need a reason for Snape to dislike Harry Potter more then anyone else.
He was never a bad person doing good things to me. He was more of a "Good isn't nice".
He was serious and stern which to me made a lot of sense when your dealing with magic (and his course could actually kill his students too. In fact it almost did a few times.)
In fact, the big part of what made Snape an interesting character is what he wasn't
I think it was the fact that he was serious and always on the ball while everyone was going crazy. He was never sucked into the "Harry Potter rules my universe" that the other characters were. That instantly made him more interesting because he HAD a personality independent from Harry Potter... even if the vast majority of his scenes involve him berrating Harry Potter.
Plus he had a certain way of doing things.
Early on in the series, I thought he would turn into a grudging accomplice of Harry Potter's, trying to do good but conflicted by his upbringing and pressure from his father to become what he was fighting against. Too bad, I guess
I kinda thought it would be two way. Harry learning to get along with people he hates, I thought he would learn not to dislike Snape, and Malfoy getting over his shallow pettyness and actually shine outside Harry's Shadow.
In fact... Malfoy is sort of a loser. When he got in the Quittage team I honestly could hear him think "Look Harry I got on the team TooooooOo, you think your so special? Well I am special too! I am special I am!"