What makes a good online course?
For me, the shorter courses are better. I like the brevity and focus.
What makes a good online course for you?
Do you mean a great video for later consumption or a really online interaction? For me former case works best when it is not video but text and latter case works when the teacher can make the experience indistinquishable from ofline work. Also there are codecademy-style courses who use gamification of learning.