This is an interesting question because it can have a generic answer but I also think people have different preferences. I've had students who like humor in class and some love someone who is more serious. A good teacher for me is a reliable teacher, someone who would love to see you improve over a period of time. In addition, a good teacher is flexible because a teacher cannot always be humorous or serious, he/she must know how to adapt to different kinds of students. Teaching is a job that requires being sociable and responsible at the same time.
Since Italki is a learning site, I am interested to know your thoughts about this.
What makes a good teacher? What is your definition of a good teacher?