A recent film I watched was "Blue Valentine" which was very good, but extremely depressing for a film that didn't feature prison or Detroit. In this film, Dean (Ryan Gosling) and Cindy (Michelle Williams) are a married couple with a small kid who are in a failing marriage. They take an overnight stay in a cheesy "sex hotel" to try and rekindle their romance, and it fails miserably, culminating in their having a fight at her job which gets her fired, and subsequently they split up. Throughout this, there are flashbacks of how they met, fell in love, got her knocked up and married--the flashbacks provide contrast to their depressing present.
What made this depressing is that there really wasn't any solid reason for their marriage breaking apart--no one cheated on the other, there was no abuse, and frankly neither character really changed much since the time of their flashbacks. Dean is still a working-class Joe, who Cindy feels isn't taking full advantage of his potential (he prefers to work as a house painter since he can drink beer at 8AM in the morning, which I'll admit is pretty sweet so lay off the guy!). Cindy is working as a nurse, rather than having become an MD as she'd wanted to (in the flashbacks), likely as a result of raising a family.
But it seems the real reason their marriage was failing was that Cindy's feelings for her husband have faded and there was no bringing them back. It was heartbreaking to see Dean trying to pull out the stops to romance her--playing their "song", joining her in the shower, boozing it up--only to see that what worked years ago just won't anymore. Perhaps if there'd been a scene where he was caught in an orgy in Bangkok while high on happy pills, it'd be easier to just point at it and say "ah, that was his mistake there"--but the film showed the realism (with excellent performances by the actors) of relationships that just die on their own, without outside help.
Never take a date to see this.