My history with the Souls series (I don't love that name, but there isn't really a better way to refer to the series) is a bit of an odd one.
My experience is that most players try out Demon's Souls and either immediately fall in love with the series forever (though no one knew it was going to be a series at that point,) or it becomes very obvious that the series isn't for them and they stay away.
I had a negative impression of Demon's Souls when I played it, and for the life of me I can't really figure out why. I think a big part of it was how deliberate the game is (a trait that has persisted throughout the series.) I don't think I was prepared for that facet of the game; most of my experience with 3rd person action games was stuff like Devil May Cry which has a very different approach to how action is handled.
Another facet I wasn't prepared for was how much the game expects you to work at it. Success comes less from raw skill and more from repetition and preparation. You may make it through some situations on your first try, but most of the gameplay in the Souls series comes from the player's ability to observe, deduce, and infer the right solution to a problem. Your character is (purposefully) too clumsy to style your way past peril and even the weakest enemies do enough damage that you can't really strong arm your way through the game either.
The final point that probably turned me off to Demon's Souls is one that I can't mince words about: this series is willfully, almost cruelly obtuse. While other games will bury you under tutorials, contextual help, and long winded explanations, the Souls series expects you to either figure things out on your own via trial and error, or go to Google and find the answers you're looking for. Items don't always have obvious uses or benefits, stats may not have obvious effects on how your character performs, and bigger numbers are not always better. It's the anti-JRPG.
All of those factors combined to make Demon's Souls a game that I wanted to like, but couldn't really get into. I had some friends that played all the way through it and loved it, but I quit trying pretty early on.
That experience always stuck with me, because Demon's Souls felt like a game I should like. I like games that challenge me; that shake up expectations; that require my attention. With the rise of the Let's Play phenomenon, I was able to track down a very entertaining and educational video LP of the game that dramatically changed my opinion of it. As I was watching that LP I realized that I had been trying to play Demon's Souls the wrong way (i.e. the way 90% of other, similar games work,) and instead of adapting and learning, I kept trying to get the game to conform to how I wanted it to play (with inevitably unsuccessful results.)
I always had a hankering to go back and try Demon's Souls again, but From Software provided an alternative: a "sequel" (mechanically the same, but no story ties to the previous game,) Dark Souls. I decided that I'd try my hand at that game, armed with the knowledge I'd gleaned from Demon's Souls. I was going to take my time with this game and learn how to play it, I'd consult outside sources as necessary to avoid undue frustration, and I'd try to appreciate the structure of the game before passing any lasting judgment.
Dark Souls was one of the absolute best games I played that year, and it's one of the most impressive, well crafted games I've ever played.
That's not to say it's flawless. The "multiplayer" components are ambitious, but not very well implemented. Weapons and stats aren't very well balanced. Pyromancy was, at least when I played through the game, very good and accessible to every player for little cost. The engine has hiccup-y moments, and the game becomes nearly unplayable in Blighttown due to framerate issues.
But all of that pales in comparison to the things Dark Souls does right. The atmosphere is fantastic throughout, even though the game takes you through several different locales. The world is amazingly well constructed; although you have to find you way on foot for much of the game and there is no mini-map, I never felt lost. The creatures you encounter are very well designed; everything from the smallest critter to the biggest boss leaves an impression. The game has an interesting story that you can find if you dig a little, but the game doesn't browbeat you with it nor require that you even know the story. The challenges are fierce but fair; perseverance and a good memory will get you further than twitch reflexes (funny for me to say.)
Dark Souls received a lot of praise following it's release, and in my opinion it deserves every bit. It's not a game for everyone, but if it is the kind of game for you it's an amazing gaming experience. From Software recognized the impact it's sleeper hit had on the gaming landscape, and put a sequel into production.
So, now we have Dark Souls II, a more direct sequel than Dark Souls was to Demon's Souls, though once again not a literal sequel (this game takes place in a similar world, but a different area with different characters.) Having spent a fair bit of time with the game since it's release (probably around 20 hours, and roughly a quarter to a third of the way thorough the game in terms of progression,) I think another title would have been more accurate:
Demon's Souls II: Dark Souls
Dark Souls II is a mix of concepts from Demon's Souls and Dark Souls. The world structure is closer to Demon's Souls - a series of sub-areas that comprise a "level" - while being realized within the more open world structure of Dark Souls (though the world isn't as literally open and traverse-able as it was in Dark Souls.) The mechanics are a mix of the sensibilities between the two games: this game has the harsher death penalty of Demon's Souls but it's tempered - Human Effigies aren't super common, but you can afford to use them judiciously, the maximum health drop is gradual instead of straight chop to 50% (making each individual death sting a little less,) and you can still wear a ring to partially offset the death health penalty (made easier to tolerate by there being 4 rings slots in this game instead of 2 in previous games.)
There's also a lot of polish that went into this game. The various stats seem to be much more carefully considered in this game (it's much harder to just focus on one or two stats for maximum gains like you could in the previous games,) the weapons feel a little better balanced (though I never play the game long enough for that to really matter,) and they seem to have a hit a nice balance between Miracles, Sorceries, and Pyromancy (Pyromancy is still easy to access, but it seems to do less damage outright and has no scaling, while the other schools of magic have better long term payout.)
Multiplayer is supposedly much better this time around, which is great for everyone that is into that facet of this series. I don't really love the idea of invasions or invading other players, though I do like the way you can help out other players (something I really need to do more of,) and I do appreciate the few Covenants that enlist you in protecting certain areas against other players. The connections definitely seem better than they were in Dark Souls and I've been connected to players much more often than I ever did in that game, so it does seem like the multiplayer infrastructure is improved this time around.
Dark Souls II is a very interesting sequel because unlike a lot of other sequels I don't feel like this game in any way invalidates the previous game. Dark Souls works so well for reasons that are well outside of it's mechanical components, so even though Dark Souls II is a big improvement in a lot of ways I definitely think Dark Souls is still worth experiencing. If someone was interested in the Souls series, Dark Souls would be the place I'd tell them to start, and look forward to Dark Souls II once they get finished with it.
Overall, I'm enjoying Dark Souls II a lot. It's not anything groundbreaking, but it's a very solid refinement of the mechanics as established in the Souls series, and I think it's probably the most mechanically sound and accessible of the three (which is still very relative to other games.) For better or worse, it feels like a sequel: the environments don't have quite as much of an impact as they did in Dark Souls, the enemy designs aren't that impressive, and the bosses (while challenging and fun to fight) haven't been really remarkable yet.
Part of that may also be that I'm still relatively early in the game, so we'll see how I feel about it after I've completed the game. I'm sure I'll be adding quite a few more ticks to the worldwide death counter before I get there.
For anyone on the fence about Dark Souls II after playing (and presumably enjoying Dark Souls), I can easily recommend it. It's a different game, but not at all in a bad way, and the differences are refreshing enough to make this game feel like a different experience (which is pretty remarkable considering how much it's cribbing from it's predecessor.)
For anyone who has had an interest in the Souls series but has always been nervous about it: jump in an try it out! Dark Souls is a fantastic game that you can get on PS3, Xbox 360, or PC, and it's been around long enough that you can probably pick it up on the cheap. Don't let the hype about the series being impossibly hard scare you away: this series is almost always difficult, but it's also almost always fair. If you respect what the game tries to teach you, you'll do remarkably well, and there are a ton of guides/wikis out there that you can use to supplement your adventure and/or help you if you get stuck. The Souls series is a remarkable experience, there's no better way to experience that than diving in for yourself, and it's a great time to do so.
If you do decide to take the plunge, I hope you enjoy yourself. It's a series that is remarkably similar to Warmachine (to tie this back to my main writing topic): every loss is a lesson, every challenge is a test of your accumulated knowledge, and though the road may be long and arduous, the final feeling of success and accomplishment is totally worth it.
Good luck, and Praise the Sun!