I must say, this is actually one of the best CGI fan creations I have ever seen, from any genre. I love the beat of the music, too.
While it is a form of CGI, it was made in Source Film Maker (SFM), so it uses the models and effects from Gmod and other source games.
Yes you can make it look better than it does in game but that doesn't change the fact that it's just a video editing program built to allow you to tinker with the environment and character models for Source engine games.
Personally, I felt like what was going on in the video wasn't...matching up exactly. I think my expectations killed it for me.