Surely it wouldn't be it couldn't be that hard to built a better youtube and seed it with quality content. I'm surprised nobody has succeeded. Is it just that the costs of serving video require an enormous company or is it that the term youtube is basically synonymous with "internet video".
Before Flash video, before html5 video, video was very difficult on the web to make work, the small yet pretty good codecs that the flash player video had were revolutionary at the time (Back in Macromedia days). Flash compression was always one of the best even though it was mostly software, still swf files are compressed/streamed in a very compact way.
Those specifically timed events won't happen again the same way, Youtube was born at the cusp of social media and the technology that made video economical enough. Youtube wouldn't be known as it is without that Flash video moment in history.