Good, but not nearly good as it could have been - After reading/playing every novel/game in the series I expected better
The game has an interesting story line, although fairly basic, which involves an Orc invasion of some planet belonging to humanity - the humans can barely hold out against this invasion by the Orcs as they are outnumbered and outgunned, and this is where you as an 'Ultra Marine' come in.
The opening scene is a-cut-above-the-rest in which it depicts you sky diving face first through debris from destroyed war ships in the planets sky and atmosphere - eventually you land on an Orc ship which is the very first fight scene of the game, and you crash this ship into some battle scarred city where war is raging.
Other than the Orcs, later in the game you encounter the Chaos Legions who come through an opened portal with their own intents, which involves killing the Orcs and humanity - making it a three-way-war, which honestly is interesting.
To conclude:
Good:
-Fun battle scenes
-Feeling of real action
-Good, simple story
-Three way war - Orcs vs Chaos vs Man
-Great war visuals and destruction
Bad:
-Battle lacks variety - same enemies consistent
-Enemies become predictable
-Ally AI is woeful
-Environment can be a bit lacking at times - too many huge corridors with nothing it them
-Boss battles are not exceptional