I enjoyed what I've played of 1. I loved what I've played of 3 (base game and bits of the first DLC.)
I absolutely loathed DS2. Wanna know why? Because when you die, your character gets weaker when you respawn. Your HP bar gets smaller. I thought that "feature" was way more unfair than anything else the game could throw at you.
I went on a spiel about it awhile ago. I agree, it's a really stupid mechanic, and the worst part of it is that because the developers assumed you're going to be running at lesser health because of the mechanic, they 1. Made the game ridiculously easier than the first game, 2. Put far more bonfires (not to mention more obvious) in the game, to the point where it feels like you're playing a Crash Bandicoot game with checkpoints sometimes, and 3. Specifically created an item in the game to diminish the effect of health loss on death (the lowest your health can be reduced to is 75%, as opposed to 50%, I think).
It's awful, and there are a hundred ways to get around it (grind to level up your HP, seek out as many effigies as you can, etc), but overall it's the very definition of a pointless, arbitrary mechanic that doesn't really add to the games meager difficulty, and instead just works as an annoyance. It rewards players for running around with reduced health, scoping out the level/bosses, and then using an effigy to restore their max health once they're confident they can complete it. That's fine, but it's just kind of stupid.
One of the reasons I loved Dark Souls was venturing into the unknown at full strength, dealing with high difficulty, and having the chance to tackle things my first try. I remember running into the Izalith spider lady and having a hard time but taking her down first try. It was challenging but it was super satisfying to pull it off on my first run. In Dark Souls 2, I probably would have been going into that situation with 50% HP, and even if I did well, the limited HP would probably spell defeat. And THEN I would run through it again at low health once or twice, figure shit out, and THEN use an effigy and make a serious attempt.
But the saddest part is that I honestly never even really used effigies in DS2... There was no point. In Dark Souls there were bosses that could wipe you out in one or two hits. In DS2 even at 50% HP almost nothing can one shot you, so if you use an effigy to get back to 100% on top of that? The game becomes a cakewalk.
Anyways, enough DS2 hate. It's still a decent game on its own, it's just a sad excuse for a Dark Souls game.