In my point of view GOT is better for it was easier to believe. There was a great variety of roles and characters compared to Witcher. What made GOT more attractive was mortality of heroes. On the other hand Witcher focuses on three characters that makes it easier to bring the plot together while GOT has multiple characters and confusingly interconnected subplots beside many attractive creative ideas such as new language. I hope Witcher be more creative, unpredictable and contain less violence and nudity.