Well when I saw the trailer for the first time I didn't give it too much attention, even being a huge fan of the game, the animation style and the main character, Vega (a playable character in Mass Effect 3), was too weak, lacking the appeal needed for an animation with the name Mass Effect on it.
But like I said, I'm a huge fan and I had to watch it. So I did. And I found myself enjoying the movie more than I thought.
Basically, Vega leads his squad on a mission to protect a colony on a distant planet from a unknown threat. When they finally strike and take all the colonists hostage, Vega has to figured out what exactly he's facing and save the colony from being abducted and exterminated, having to make some tough decisions on the way.
The catch here is, if you have played Mass Effect 3 you already know what will happen in the movie, as Vega himself can tell you that in the game. And that may be the biggest mistake with this movie. This should've been released when Mass Effect 2 came out, back in 2010. It would make a lot of more sense, as the story here happens few months before the second game's story and would be a good surprise to see Vega in the third game after seeing this movie back then. Oh well...
The animation is pretty average. There's blood and lots of action, but the style they used just doesn't fit to the Mass Effect universe. It doesn't work. Why use Anime style on this anyway? Seriously. And not a great one too. It lacked something, I can't tell exactly what. They did the same mistake with Dragon Age animated movie. EA got it right with the first Dead Space animated movie. Please, go back to that. Mass Effect deserve way better than this. But that's just me, I'm sure there are many people that will enjoy it, I suppose.
All in all, this movie is mostly for fans of the Mass Effect game series. If you've never played the game, you may still enjoy this, but without knowing the universe it just wont be the same. It's a good movie, average animation, good story, but it could be a lot better. Its not enough to have the Mass Effect name on it.