Not the best, but good
That wasnt bad at all, I definitely liked the music (System of a Down?) Tt matched the "ass kicking" theme of the Space Marines very well. The animation was a little cheesey but still a lot better than I could ever dream of doing, but it managed to illustrate the point in a good style and that's what matters. I liked how you incorporated them fighting a few of the evils from the Warhammer 40k universe, Necrons, Chaos Space Marines, Orks, though I felt it kind of lacked a large scale battle against impossible odds that the Space Marines are known for which would have been neat, but I understand the limits of animation.
Final Judgement: It was good, not the best, but good!