Deep within, Snape is a good guy. Snape was close friends with Lily when they were kids. James Potter bullied Snape. How would it feel to lose the love of your life to the person who bullied you as a child? Yes, it was wrong for Snape to bully Harry, but his ultimate goals were good. I entirely agree that it is not right that Snape bullied Neville, but how would it feel knowing that the person you loved could have been saved if a different decision was made? (Neville being the chosen one instead of Harry). Snape never got over losing Lily, shown by his Patronus. Some of Snape's choices were not the right ones, but he made these choices in pain from his lost love.
Snape saved Harry Potter's life multiple times. Snape tried to stop the curse Quirell was setting upon Harry in the first book at the Quittich Match. He also tried to save Harry, Ron and Hermione from the werewolf form of Lupin. Those are only two examples, but there are many more.
Snape aided and abetted Voldemort in multiple counts of murder including Harry's closest thing to a father: Dumbledore. He did nothing to stop Voldemort despite having multiple chances to just because of some stupid prophecy. He had free will he could choose and he chose to not stop of all that madness that does not make him a "Good guy". His final acts saved him from being a straight up bad guy, but good guy? No.