Winehouse and Cobain are not really that comparable. Cobain turned to drugs after he became famous as a way of escaping a life of fame that wasn't what he thought it was going to be. Winehouse was an addict before she even became famous. There are similarities but let's not go overboard with the comparisons, they are separate individuals.
Never was a fan of her music, and I don't feel a lot of sympathy for her specifically. She was given every chance in the world to get well and simply didn't want to, so I feel like she's basically gotten exactly what she signed on for. I do feel bad for her family though, I know her parents have tried repeatedly to get her help and it must be just awful for them to have this happen despite all of their best efforts. Some people just don't want to get well and she, unfortunately, was one of those.