what makes a good language learner? this is an eternal question to which there is no real answer. so everything i am going to say is open to discussion.
motivation is certain[y to be the most important factor. there are two types of motivation. one is external motivation--this is the kind of motivation that persuades a student to learn a language in order to pass an examination. the opposite of this is internal motivation, which is to master the language more rapidly so that it can be used as a tool in future work.personality is another major factor. i am not necessarily saying that one needs to be out going but someone who has the confidence to make mistakes can learn much more quickly than someone who is afraid to experiment.
intelligence isn"t a factor in language learning i would prefer to use the term language skills. learning skills are those abilities that allow a learner to progress faster than others; they include having a good memory, having a good ear, efficient revision and suitable organization of learning gradually.
what i believe is the most important factor is independence. a learner who is independent of the teacher and who accepts responsibility for learning is always going to be not just a good language learner but the best.