Warhammer 40,000: Space Marine
The combat is a little more sophisticated than is apparent in the demo: there are a few weapons to swap between - notably, the warhammer's slow, brute strength changes the melee mechanics somewhat - and situationally-available guns that are pretty great, like a laser cannon and a heat-shotgun. And some enemies do actually demand different tactics, ... but this is where the game can get a little messy.
As the campaign marches on, you'll encounter enemies who can do increasingly ludicrous damage from range: devastating mortar launchers, disturbingly strong machine guns, lightning laser beams, and grenade spam will annihilate you handily unless you're well covered. Granted, this isn't "supposed" to be a cover-based game, but while it's easy enough in the early chapters to charge into a horde of enemies and start mopping them up, later on this tactic is suicidal.
It doesn't help that Space Marine's execution-system, which is built to allow you to stay in the thick of melee combat, is fatally flawed in the presence of enemies who can do great damage, and/or who can attack from range. Captain Titus can refill his health by stunning and then executing enemies, but he will still take damage - and can even be killed - while the (lengthy) execution animation is playing. So while you're cutting one guy's head off and waiting for the health bonus, another nearby enemy might shatter your health bar with a single large attack, or a half-dozen dudes with guns might just whittle you down unopposed.
In the last wave of the waves-of-enemies-based final boss battle, I actually died while executing an enemy because another enemy just dropped a grenade at my feet. Since the execution takes so long, and there's no way for me to move, or cancel it, there was absolutely nothing I could do. (And since the game rarely saves checkpoints between waves, I had to start back at the first one again. Which I did about fifteen times, before giving up and restarting the chapter on Easy mode.)
When the game works, though - that is, when the number of enemies you're fighting is manageable (or when you have a jetpack and can just dive-bomb them) - it can be pretty fun. There is a little depth in terms of choosing which enemies to toss bullets at, when to charge in, and how to balance melee combos between stunning and finishing enemies. But in general it derives its simple joys from running headlong into foes and smacking them around.
Also, the campaign is pretty short, which is really to the game's benefit -- it already feels like it's stretching its premise a little thin. As long as your expectations aren't too high, you can make a fun weekend out of it.
For a studio that's only known for its real-time strategy games, this is a fairly competent first attempt at an action/shooter formula, and it's interesting to think of how they'll evolve their ideas in the inevitable sequel. But within the action and shooter genres, Space Marine is generally unremarkable. Its controls are solid, but it too frequently avoids genuinely interesting combat encounters by throwing out wave after wave of enemies. And while the guns are fun to play with, the lack of a proper cover system significantly limits your opportunities for dealing damage without dying instantly.
Better than: Conan (2007), Dark Void
Not as good as: Darksiders, Vanquish
Launching without co-op: is kind of stupid, right? Who's going to care about this game anymore in October?
Progress: Finished on Normal (except the final boss, on Easy)