And part of the problem with asking "what's the best lecture on x" is that the replies often come from people who have seen one prestigious lecture, and recomme

And part of the problem with asking "what's the best lecture on x" is that the replies often come from people who have seen one prestigious lecture, and recommend the one they are familiar with. Popularity breeds popularity. There's a much smaller sample of people who sat through 20-30 of the same lecture series, for the same course, from different professors, and know which parts are the best from which person.