YouTube is the most well-known video service on the Internet. YouTube lets anyone share videos online, either from their hard drive or recorded using their computer's Web cam. It uses Flash and a simple video player that starts playing videos right away. While the quality isn't that great, it's become incredibly popular for the sheer amount of content that's made its way onto the site from its massive group of users.
YouTube has paved the way for a variety of other services and evolved its own services with new features such as user profiles, video rankings, and a system that lets anyone reply to a video either with text or another video. It's also introduced some controversial features such as video viewing history, and displaying who's watching a video at the same time you are.
Winner: YouTube (YouTube.com)