I think Grey's has some of the worst writing i've ever seen in a tv show. I've only seen like four episodes, but they were all awful. Everyone always says "oh well that was just a bad episode, the rest are better"...i'm sorry but if you randomly pick four episodes of a show and they were all coincidentally the "worst episode", the show sucks, end of story.
I always found House entertaining not for the medical part but just from the characters being funny, but it has definitely gotten monotonous. They tried to change it up this year with all the different fellows, but it's just not for me. Now i watch it cuz 13 is hot, and an old habit is hard to break.
Nip/Tuck has nothing to do with medicine, although they are plastic surgeons. That said, it is the most F'ed up stuff i've ever seen, the twists they have there. It's so perfectly unrealistic, i love it. I'm sick of the reality television fad, i don't want to hear things that stupid people would really say, i want well written ridiculousness. that's why gilmore girls was so good.