Wait a second, are you inferring that the first one wasn't great? Or just that the sequel has to surpass an already great game?
I have yet to play Darksiders, so I can't comment on my personal thoughts, but from what I've heard from most sources it's really not an amazing game. Definitely good, but not amazing. From what I've seen of it, I agree with them. Again, dunno if my thoughts may change when I play it, but I'm just making the point that... yeah, a lot of people really didn't feel the original game was that good; you're probably going to hear people saying that a lot,
especially if Darksiders II is a better game.
Death really is an anti-hero of sorts, and many fans probably could originally relate to him. Death, or the Grim Reeper, is often times the bad guy or big boss in many video games, yet here he is as the main playable character. Visually I think I prefer War, but that might be just because I've seen him in action with the first game. We'll see.
I don't see, from what the trailer shows of the storyline, how Death is any more of an antihero than War was. I get it that War was kind of supposed to be that, but he was pretty much the hero because he was falsely accused, correct? He's just darker and more stereotypically "evil" in appearance. I like him better visually myself, but I can't comment on his personality yet. (I'm also curious if, throughout the Darksiders series, we'll end up playing as all of the Horsemen.)
Also, just for the record, I think the notion of death being evil is a product of fairly closed-minded early entertainment, in which everything creepy in any way has to be evil. As I gather the Four Horsemen were never supposed to be evil... just a bad thing. A elemental force of destruction, as opposed to malicious entities. I've seen many, many more depictions these days in which Death or some kind of representation of the Reaper isn't portrayed as evil... which is good because that's a lot more accurate than turning him into a badguy.