This one isn't obvious, but think about it. The Doctor is a Timelord. To him, we are very alien. Out of everyone on this list, the Humans are probably the most important. The Doctor seems to have formed a sort of bond with us over the years. He is constantly spending time with humans, teaching them and sometimes saving them. The first Doctor would doubtless call the eleventh Doctor soft, of course. But as stupid, rash, emotional and apish as we may be, he still took a liking to us.