The main point is that Harry had the belief that he HAD been loved. He knew he had parents, and even if those who raised him didn't tell him his parents loved he, he thought that they probably did. This is canon. I believe Harry mused over his parents' love for him several times. Snape knew for a fact that he wasn't loved or cared for by his parents. There is a big difference between holding out hope that someone has loved you and knowing that no one ever has. And that's a difference big enough to account for the behavior difference in Harry and Snape.

I don't remember it being mentioned anywhere that Snape's mother gave him the nickname Prince. It was simply her maiden name. I think it comes across quite clearly from the early memories that he received little to no affection as a child, especially in his reaction to Lily and Petunia.

At any rate, I don't see either of us changing our minds about this. Snape is doomed to be considered an asshole by many, and a romantic hero by many more. I'm somewhere in the middle. I appreciate him a character. I still like him a great deal, even with the flaws. However, I don't deny that those flaws exist. I just seem to have a bit more sympathy for him than the haters and a bit more realism than the lovers.

I'm sure this debate could go on for ages, but I'm going to end my part in it right here. Ta ta!