I'm quite a fan of comedy, even if the subject and story are essentially very bleak, I think a little bit of humour can totally throw you and make you more sympathetic. it's been ages since I saw requiem for a dream, maybe ten years, I remember scenes very clearly though (teeth grinding bit, speeded up sequence, the choppy drug taking bits and god, the whole last 10 minutes when everyone is getting the worst) but I don't remember really caring about the characters.
have you ever seen any Pedro Almodovar? He's one of my favourite directors and he's got a few films which are quite bleak but they're a bit more surreal with touches of humour but I think that makes me care about the characters a lot more. They're in spanish though so it depends if subs are for you. All About My Mother and The Skin I Live in are really good.
never seen the butler, I'm a big fan of forest whitaker though so I'll keep and eye out for it.