I watched Requiem for a Dream on DVD--or watched parts of it. The DVD itself starts out promising enough; they have it set up like the layout of one of those mail order commercials at the end, and for just a minute it was confusing. That is, they show a commercial--right down to the tiniest bit of interference on your screen--and then go to the menu, which looks like the instructions for ordering the product. Effective.
Once the film started, it still looked like it would at least be originial, if mannered (some speeded up shots, split-screen between two scenes, rapid juxtaposition of images to mimic "tripping"), but I eventually started hitting the fast forward button. Perhaps I'm not totally qualified to review it in light of that, but I thought overall it was one of the worst films I've seen.
It had Jennifer Connelly in it (poor girl), so maybe that's why I had it in my queue. Then I checked out the reviews and Rotten Tomatoes has 70 percent or better as positive, many of them glowing. So I must have read a praiseful review, too--Ellen Burstyn's performance draws high marks from several.
Nevertheless, provided your idea of a good film is not one in which the main characters are tortured and degraded throughout and to no redeeming purpose, avoid this film like a gangrenous limb.