The best one I ever saw was in an Israeli movie called "Late Wedding". Here's a good description of the scene from Kinocite:

Their love scene early in the film is remarkable in its naturalness, forgoing gratuitousness to instead establish the intimate physical and emotional bond shared by the couple. And in a vast departure from Hollywood sex scenes, this one serves to make the eventual heartbreak that befalls Zaza and Judith seem all the more real.

There are also good sex scenes in many French movies, but I can't really remember which ones.