As far as mainstream movies go and explicit sex, then the Danish movie 'Daisy Diamond' with Noomi Rapace is up with the best.
http://www.imdb.com/title/tt0839773/?ref_=nm_flmg_act_22
It's not an uplifting movie at all though, it's dark and depressing as can be as it tells the story of a single mother doing whatever she must to get a job in the acting business. She ends up doing porn and for my money, outside of real porn, I've never seen such explicit and real looking scenes. This was made before Noomi Rapace made it big in Hollywood, otherwise I doubt she would ever have consented to being filmed shaving herself - nice frontal views - and having sex with various men in various positions.
But as I said, it is depressing as only a Scandinavian movie can be and afterwards, despite the very explicit sex scenes, you'd be pardoned for wanting to take a vow of chastity.
But even if you just skim through the movie and look at the nude scenes only, it's worth it as Noomi rapace is a very beautiful actress.