Both Goro and Yusuke are VERY good boys! They're actually my top favorites in the game. But I am a bigger fan for Goro so I have to say that Goro is best boy (in my opinion). All these boys are best boys though!
As I am typing this i am laying on top of my Yusuke body pillow. I feel comfort as if i am really in the arms of Yusuke himself, I bring this to you in hopes that you will reach the same plane of thought that i am on, and that yusuke is best boy