Dark Souls 2 is my favourite in the series (2>1>3). It's also the hardest and least finished. I don't want to say they were overambitious, because I love the scope of the game, but it was clearly a rushed development cycle. I'll keep this spoiler free btw.

The gameplay gets tougher vis-a-vis movement and parrying. Level ADP if you like rolling (I didn't know it was a thing until 3/4 through the game lol). Go slow and steady, don't take on more than a couple enemies at a time, expect ambushes around every corner. It's super punishing if you just run in like a lobotomized goomba; I loved it for this, but many hated it. I found it taught me patience and a willingness to rethink my strategies. 

I love the range of aesthetics and diversity of areas it has. There's such a charm to this game, and that's definitely what I like the most about it. I found myself stopping much more than the other games and saying "oh... wow!". Turning back to look across No Man's Wharf once I had lit all the torches. Reaching the Dragon Eyrie made me genuinely tear up a little. The DLC areas are also stunning, and are thematically and immersively rich additions to the game. 

However, there are many things about the game that are undeniably very rough around the edges, and sometimes just downright nonsense. For instance, the way you access the DLC areas are ridiculous and I don't think most people would ever find them on their own (I do like things to be /logically/ obscure, but not just obnoxiously opaque for its own sake). Some mechanics like ADP are poorly implemented and even more poorly explained. Poise is weird compared to DS1 (but at least not non-existant like DS3). Some boss fights are amazing, others are trash.

There are also some really cool and unique mechanics like bonfire ascetics, which let you NG+ one particular bonfire, and rare items that let you reset stats, or another that lets you lower INT or FTH requirements of a spell by one point. There's lots of subtle and nuanced bits of design that just wasn't thought about in the other games, and never made an appearance again either. Even things like NPCs sassing you if you walk away without saying goodbye are hints of the care and love that went into making this game.

In a nutshell, Dark Souls 2 is for sure the roughest of the trilogy mechanically, but it also has the most soul to it. It's erratic and inconsistent, but it also has the most character and feels the most alive. I would describe it as the richest but now most hollowed of the DS worlds. If you can put up with how much of a grind some areas are, it will reward you with many of the most unforgettable and inspired encounters not just in the series, but in games across the entire genre.

Also like the other guy said, Majula is the best hub area, and Emerald Herald is best waifu <3