This animated Half-Life 2 clip isn't your average piece of amateur machinima. It's a cinematic trailer put together by Marco Spitoni, who works at WETA, the guys behind the special effects for Lord of the Rings and District 9.
And doesn't it show. If someone was ever to make a full animated movie in this style, ala Beowulf or Final Fantasy, this is exactly what it should look like.
Spitoni has made a few other equally-impressive shorts, including a Star Wars recruitment piece, that you can check out at his site.