Youtube Street Fighter kicks ass
This Youtube Street Fighter video falls into the many categories below, all of which helped it become "viral".
1: Looks like it took a lot of time to put together
2: Done for fun and not by a brand
3: Taps into a popular culture (gaming)
4: Taps into a popular sub culture (stop motion animated toys)
5: It's the first time it's been done (original)
6: Well produced but not over done
Take a number of these away and you have is a "fail" video.