I disagree. Witcher 2's sex scenes are hilarious but tasteless. They characterize the world and I find them to be a necessary evil, but I get nothing out of them other than a boner. (except ew, they have dead eyes post-sex in all scenes!)
Witcher 2 does sex better depending on what your viewpoint is (better animations) but the actual romance is something I don't feel. There's nothing romantic about telling Ves she's pretty and "let's hook up!" and then, BAM, SEX SCENE. Triss' one is very romantically erotic but again, it's all about raw sex and not their mutual love.
Bioware is also steadily getting ahead of CD Projekt when it comes to explicity and animations. The fact that we almost get to see them have sex (Cass Roamance or Cullen) plus they're finally naked is a great step up. I don't personally need to see video-game PG-rated scenes like in the Witcher. Like I said, I find it more hilarious than tasteful or beautiful even.
You could put it simply: Bioware are good at mature romance writing. CD Projekt likes naughty and sometimes immature romance that's all about sex.