For some good conferences, these were the conferences with most talks in the top 500 talks, the number of talks & video link to top talk from that conference.
TEDxTokyo,24
TEDxBuenosAires,18
TEDxCairo,17
TEDxParis,17
TEDxDubai,14
TEDxCaltech,12
TEDxNYED,10
TEDxEast,7
TEDxLahore,7
TEDxTaipei,7
I wrote couple of Python (programming language) scripts that used YouTube API. The approach, find TEDx conference with a larger number of high quality talks, the quality measured by view count.
Some additional notes:
-A check in top 200, brings in TEDxBerlin, TEDxCMU, TEDxNASA & TEDxToronto
-A check in top 1000 brings in TEDxSF, TEDxAmsterdam & TEDxAcademy
-The code is bunch of small Python scripts and is in github at https://github.com/amitch/ytube-tedx