As great as their intrigue is that's how bad GoT handles its romance. Tyrion + Shae = cringe and I don't buy it from either of them. There's I guess Jamie and Cersei romance?

Robb and Talisa was mostly just weird. They had a moment with Talisa lying in her bare ass for 10 minutes which did manage to show her as being desirable but other than that she just seemed to cause problems while bringing nothing to the table herself. Jon and Ygritte, I could buy it from her side but not from his. Which in a way could classify as accurate acting because he betrayed her the first chance he got but it doesn't make for good romance. Ned Stark and Catelyn seemed like a great couple though.

My guess is that all the drama and perversions don't leave room for any genuine romance, romance in GoT is just an device to move the plot forward. That's why it can't convince.