Yeah, I wanted to like Ultramarines (I think Abnett wrote the story) but it just fell so flat.
Watched Ultramarines, which apparently is an official Games Workshop Warhammer 40K movie. It's like a long cutscene from a pretty generic game, but where even a generic game might involve you in some way, the movie just leaves you to watch.
The graphics and animations switch between okay and terrible (the spacemarines look like plastic game miniatures most of the time, which doesn't do much for immersion, and there are some weird scenes where depth of field and such is screwed up so it feels like you're looking at toys. That could be on purpose, I suppose, but if so it doesn't work very well, especially not when other scenes look decently realistic).
I'm not an expert on W40K, but it seemed to me there were also a number of things that weren't true to the mythos.
The intro cutscene in Dawn of War made me feel a lot more than this movie did.