What struck me immediately about Darksiders was its story. It's not often that you come across a game based in Judeo-Christian mythology. Outside of the occasional Japanese Anime or J-RPG bastardizing the myths, it simply isn't done. Darksiders not only had the balls to design an entire game around it, but actually injected enough into the mythology to create a story that was wholly new and refreshing.
*If you haven't played the game, or simply don't want to be spoiled, stop reading here. You have been warned.*
As mentioned above, the game takes elements of the apocalyptic myths and Book of Enoch and tells its own story. Humanity, the "Third Kingdom," was lost during the Apocalypse, and Hell defeated Heaven during the battle. War, the protagonist of the story and Horseman of the Apocalypse, was betrayed into believing he instigated the battle, and does everything in his power to prove his innocence. He is allowed to search for clues (stripped of his powers and under the Council's constant surveillance) on a decrepit and ruined Earth, and the rest of the game follows.
The game plays in what is essentially traditional Zelda fashion, in which players use their abilities, weapons and sub-weapons to explore and reach new areas, only to acquire more weapons and abilities which allows them to in turn reach more areas, etc.
What made Darksiders strong was the fact that your abilities, weapons and sub-weapons all had a distinct purpose, and all of them were useful for both fighting and for exploration. Zelda has fallen behind in this respect. Too often you get useless shit that you use once on your adventure and then leave in your inventory to rot.
Not so with Darksiders. The Crossblade was useful for keeping combos alive and juggling opponents, in addition to hitting switches and such. The Abyssal Chain was useful as a grappling tool in combat, as well as for exploration. The Tremor Gauntlet gave War some stupidly powerful attacks and helped demolish debris and crap in his way. Hell, the Scythe, the sole purpose of which was combat, was useful for getting more money (Souls).
This was Darksiders' strongest point on the adventure/exploration front: the versatility of the sub weapons. This needs to make it into Darksiders 2.
On top of this, War had some nice timing-based combos, a la Devil May Cry. Do a standard combo by pressing attack four times. Do an extended combo by pausing after the second slash. Do yet another combo by pausing after the third slash, etc. This method clicked with me because of its simplicity. You don't need to press different buttons to execute different combos: you get a great variety of attacks through one button.
I loved this aspect of combat, and the addition of another input (like say, back - forth on the analog stick + attack) wouldn't hurt in a sequel.
The only thing I can say I didn't like too much about combat was the aerial gameplay. Comboing enemies in the air looked cool, but could easily get you nailed. Enemies could still hit you while you were in the air, making it flashy but not at all useful. This was a shame because War came equipped with a easy-to-execute launcher (holding the attack button) and a basic aerial combo.
Devil May Cry 3 and 4 remedied this by making most enemies heavily ground-based (they can't touch you in the air) and by allowing Dante to jump off enemies while in the air (for a quick escape in a pinch). Bayonetta remedied aerial impotence by allowing you to dodge while in the air. A basic feature like this could go a long way to enriching the combat in Darksiders.
Darksiders also lacked competent enemies. Much like the demons in Devil May Cry 3, the enemies in Darksiders were aggressive, but not particularly dangerous once players recognized their telegraphs. War has a block and a dodge: enemies should have counters for both, so that players need to rely on one or the other to avoid taking damage from particular attacks. The same enemy should have attacks that must be blocked to mitigate damage, as well as attacks that will break through your block and must be dodged to avoid damage.
The timing for a player's reaction should get tighter as the game progresses, too. Bayonetta gives you one defensive maneuver: dodging. That's it. But the timing for that dodge must be precise, because different enemies have different attacks that must be dodged at different times. Hell, a single enemy has different attacks that must be dodged at different times. This makes enemies more versatile and unpredictable, and keeps players on their toes. And if the controls are responsive, this makes combat tighter in general.
All in all, I though Darksiders is a very good Action-Adventure title. Combat was enjoyable, as was the exploration and adventuring.
In truth, I really want to see the story of Darksiders continued. We never find out what happens to Samael, who the woman was that corrupted Abaddon, what actions the council would take against War, and what War and his brothers would do now that the truth was out and the Seventh Seal was broken. I read that Darksiders 2 would focus on a new character, and while I'm a bit disappointed to hear this, I hope some of these questions are answered.