Is it sin to dislike dishes cooked for us and to be picky about dishes?

It is not sin to like some dishes better than others or not to eat some dishes. However, it is not appropriate to disdain or speak ill of any food or dish. 

The Prophet (pbuh) did not ever disdain any food or dish that he disliked publicly and also prohibited others disdain. He emphasized that it is necessary that people behave respectful to other people’s choices and prevented foods from being wasted away by saying “Leave what you dislike. Do not make it haram for others.” 

What the Messenger of Allah (pbuh) looked for in a dish or food primarily was halal-ness and cleanliness and whether it was beneficial to body or not. He never had the habit of being picky about food and disdaining them. 

Abu Huraira says: 

“The Prophet never criticized any food. He would eat food given to him if he was hungry or leave it if he was not. Especially, when he was guest in someone’s house, he would compliment the host about the food offered and express that he liked the food offered a lot.”