If you only have one or two videos uploaded your chances of getting accepted are low, even if those videos went viral. That's because YouTube is looking for people who are planning to work with them over the long term.
The more regularly and frequently you upload new videos, the better. For instance, someone who uploads a new video every day will have a better chance of getting accepted than someone who uploads one every couple of weeks.
You also want to make sure you have at least 100 uploaded videos before applying to become a partner (though some people say 50 will be enough).
