Gemara requires a particular type of mind to be completely successful at it

there are many other areas of Jewish study that are worthwhile

Bible, Halakhah, Jewish Thought, etc

The Netziv (Naphtali Zvi Yehudah Berlin had trouble with Gemara as a youth yet grew to be the "last" Rosh Yeshiva of Volozhin

Motivation to learn can often be tricky. One of the greatest factors in motivating someone (especially children and adolescents) is value of the learning relationships or the social factor rather than the subject matter itself. The most significant contributor to the social motivation in learning is the teacher. Students often love subjects because they love their teacher. Who the teacher is and how he is relating to your son (even if it’s you as a parent) may be worth exploring. Research shows that if the teacher is a positive and desirable role model to the student, the student will be motivated.

 

Another contributing factor to motivation is whether the subject matter is relevant to his identity. Children – especially adolescents – are working hard on developing their personal and social identity. If the material he is studying in the Gemara is not compelling to what is relevant for him personally or socially, he may not be motivated to learn it. I can relate to this. There are times I found sections of the Gemara tedious and irrelevant and then years later, I rediscovered them and found them very interesting. What he is studying in the Gemara may be a factor.

 

Finally, it just may be that he needs a break. Sometimes we have to let something go of something for a bit in order to genuinely appreciate it, i.e., we don’t know what we’ve got until it’s gone. Teens and young adults who are forming their identity will experiment with different personas as they are sorting out who they are. Resistance to learning Gemara may involve something very significant about his identity such as his relationship to Judaism or his relationship to you as a parent. Or it may be something far less significant, such as that he wants to dedicate all of his time to reading about American history or baseball or parshanut.

 

Whatever the case may be for his lack of motivation, it is important that you as a parent show that you love and accept him yet that you are also still committed to your principles of the value of learning Talmud. He must be given space to appropriately express his independence and the ideas and feelings he has as a human being, but also understand that he has responsibilities to you as a parent, to his school, and to his Judaism.

 

Judging by your question, it seems that your son is old enough to be able to understand a blatt Gemara and that his Hebrew and Aramaic are at that level, not to mention his ability to follow the arguments.  If that is not the case, then it seems pretty clear why he is not interested.  Reading something that is indecipherable and not particularly engaging, regardless of how we feel about it, is a frustrating proposition and there is little that can be accomplished by pushing.  

 

So I will assume that he is old enough to be able to read and that he is a young adult.

 

You may not be surprised that an entire movement of Judaism was formed in response to this same issue: namely, Hassidism.

 

The Jews in the East of Europe prided themselves on their yeshivot and institutions of higher and sophisticated learning.  They tended to look at Eastern Jews, the Jews beyond the Pale of Settlement, as country bumkins.  They were, in the minds of the German, Western Lithuanian, Western Polish Jews, and so forth, ignorant and silly.  In response to the yeshiva learning of the Jews of western Europe, the Jews of the East sought God in a non-traditional way  - they sang and danced.  Joy in Torah is found not just in the books of the Jews, but also in the heart of the Jews.  Yeshiva learning was made secondary to a joyful Jewish life.  In fact, each group saw themselves as the true expression of Judaism and the other group as heretics.  

 

Your son is exploring his 'Hassidic' side, if you will.  He is not engaged in the Gemara and no amount of pushing him will get him to be engaged.  You are a good role model by learning.  Learn with him, but also ask him to share what he is learning with you.  It may not be Gemara but it will be a bridge of learning that the both of you can share.  If he thinks that you believe that only Gemara is the Jewish way to learn, he knows he will disappoint.  Therefore, reach out to him and learn with him.  You will both benefit.