Let me take you back seven Hogwarts years. I loved Snape from the moment he was introduced, you know, ever since when Harry saw him in the Great Hall and his scar hurt. The malicious, badass Slytherin professor who does everything in his capacity to make Harry's life miserable, and in spite of being described as greasy-haired and icky, is portrayed by Alan Rickman. What's not to like?
Actually, it's not the part where he turns out to be on Dumbledore's side that bothers me. That's one 'twist' we all sort of expected; I mean, you didn't really think he fooled Dumbledore, did you? I wish it wasn't because of love though, because a mushy love story just doesn't fit in with such a badass character.
It's funny how Snape suddenly goes from 'an adult who bullied you, not to mention all your friends, for seven years' to 'a great man you ought to name your kids after'! And all because he had a crush he couldn't quite get over.
Sure, he loved Lily. I bet Lucius loved Narcissa; doesn't make either of them saints. Did everyone who read 'The Prince's Tale' not read 'Snape's Worst Memory'? When James Potter was a troublemaker, Snape was a budding Death Eater. Did he not care about Lily when he turned into one? And when he told Voldemort about the prophecy? When he asked Voldemort to spare Lily and just kill her child? And in Hogwarts, after supposedly turning super-good, it wasn't just Harry, whom he bullied. Snape tortured every person he set his eyes on who wasn't a Slytherin.
Snape wasn't evil, true. He stayed loyal to Dumbledore till the very end. But he was definitely not the hero he is made out to be. I mean, think about it, if it had turned out, that the prophecy was actually about Neville Longbottom, Snape would have switched loyalties in a heartbeat...