Great topic, great forum! I'm excited!

I don't think his ability to love Lily made him a good person. Neither do I think that his youthful choices to participate with Dark arts-- the only folks who accepted him, for what it's worth -- made him a bad person. Many have said it and I'll reiterate- people (and well drawn characters) are rarely so black-or-white. Even Dumbledore... we tend to forget that he was hardly an 'all good' guy, and I think he recognized a lot of himself in Snape, which is why he was able to trust Severus when no one else quite did.

Snape's true character is evident in his ability to eschew the doctrine of hate and violence that the death eaters and Voldemort embraced and risk his own safety to stop the genocide and terror acts that caused the death of his own unrequited beloved and countless others. Would he have given up on Voldemort's campaign and turned spy if not for Lily's death? Possibly not... but maybe he would have. Something else could have caused him to change his perspective, because he had a conscience. I'm not saying he was a greasy Snape treat with a completely fluffy marshmallow center. He was often abusive and often unfair, petty, and very wounded.

But he was compelling, redeemable and sympathetic -- not for his ability to love so much as the fact that he displayed an active conscience and therefore grew in his personal arc as a result.

I contend that therefore conscience, not love, was his salvation and made him a... well, not 'good' person, but a person with redeeming qualities.