I actually didn't intend to play this game at all. However I had already finished Darksiders 2 and Borderlands 2 was more or less around the corner. Not enough time to play any of the games I had particularly planned to (Dragon's Dogma for instance) but enough time for some quick playthroughs and I just happened to find this one for next to nothing in a supermarket. I used to be a Warhammer 40k player so the subject matter did have some meaning to me. In a nutshell, that is what keeps Space Marine going really. The game captures the feeling of the ultra-dark 41st millennium. The protagonist and his two pals feel are very much in canon to the grim lore; getting to massacre orks with familiar tools of destruction like bolters, chain swords and even freaking lascannons and thunder hammers has a certain oomph that generic no-name shooters would lack.
The scene towards the end of the game where reinforcements finally arrive and storm a chaos-infested bridge together with the player almost brought a tear to my eye. It also made me wonder why there wasn't more of this in the game. Most of the time the player hangs with just his two pals (who seem to be immortal) and they explore all sorts of industrial complexes like in any bread-and-butter shooter. Most of the best scenes in the game are ones where imperial guardsmen are involved because it immediately feels more like war. That's kind of what you would expect from a WH40k game: war. There's a plot in the game that kind of justifies the level design. As far as plots go, I guess it is fitting and does give the designers a solid excuse to get the player to shoot chaos marines, cultists and infantry instead of orks for the later part of the game. Oh, and also witness orks and chaos shooting at each other which is also cool.
Still I feel like less plot - more battlefield would have been a better solution for this game. Nevertheless, the bodycount reaches hilarious numbers - I really wished there would have been a kill counter in this game. In many scenes the green stream of orks is almost neverending. Most importantly, they die with satisfying amounts of violence and gore. Melee finishers especially are ridiculously brutal. The Emperor's justice is ruthless. The way theme is handled is the biggest strength of this game. It also means that people who don't give a rat's ass about Warhammer won't get much out of this game. Without the theme Space Marine is just a pretty average action shooter/slasher with huge waves of enemies.
The game's control scheme was a bit weird to my taste. Normally shooter/slashers have a separate aiming mode; outside it, the character faces the way he is moving. Space Marine does this a bit weirdly because the aiming mode is always on and the character is facing at whatever he is targeting. Until you press a melee attack, at which point he slashes at whatever direction the movement stick is pointing. This is really confusing at first. Then again, melee in this game is more or less button smashing, so the controls don't create much frustration. I still have to wonder whether they should have done the usual thing and separate melee and shooting modes from each other.
The game doesn't have any silly things like crouching. Who needs cover when you have a power armor? Health regen is Borderlands-y; armor regenerates but health is only recovered by delivering the Emperor's justice via killing blows. The coolest single gadget in this game was the jump pack. It sounds pretty boring but they've really buffed it up. It doesn't just allow quick vertical movement but also enables powerful dive attacks that are guaranteed to crush anything on the immediate landing spot and push others way back. Most importantly, targeting these dives is easy. It's a great change of pace whenever it gets used in the game (two or three times total I think), and when combined with the almighty thunder hammer the jump pack becomes even deadlier.
While Space Marine offers even less new things than Darksiders 2, it's yet another reminder that subject matter matters. The grim and dark future of the 41st millennium is for many people the ultimate setting for hilarious bodycounts and senseless violence.