I first tried the original NG 2 by a friend, since I don't own an Xbox. My first impression was "fun, but a bit too chaotic". However I bought Sigma 2 for my ps3 and played it twice, but I never got really deep with the mechanics. The best thing about it is the core combat, that's for sure. I love the weapons (especially claws, tonfas, scythe and kusarigama, but seriously all of them are amazing) and I find the delimb system SOOO satisfying. What I didn't like was the ranged enemies attacking from off-screen, and some bosses (I know that bosses are not that important in this series, but does anyone genuinely enjoy fighting the water dragon or the metal worm?). Overall still a really solid game.
Later I did some research about the differences between 2 and Sigma 2, and came to the conclusion that I prefer the latter. I don't care about the gore, I like the new female characters and I'd probably get frustrated half of the time with OG 2, which seems even a lot more unpolished. I can kind of see the appeal of a game such as that, but I don't think I would enjoy it that much.
That being said, everyone online kept talking about how 1/Black/Sigma was the better game, and not at all unfair unlike 2, so I bought it (the Sigma version). The result was... quite disappointing actually, but I know I dismissed the game too quickly. The combat felt watered down because of the lack of delimbs or flashy movesets, and I didn't think it was perfectly fair and polished. I mean, the horse enemies in Chapter 2 were all but enjoyable for me. However, I dropped the game in Chapter 3.
That's it, so basically it's a series I've never really delved into and I have a love/hate relationship with it. I plan to give another chance to Sigma, because I know it deserves it, then replay Sigma 2 and finally buy Razor's Edge, which also seems to be pretty different from the other two, yet shares the same core.
However I really think that Team Ninja doesn't really know (or chooses to ignore it) what separates a fair and fun challenge from a chaotic and unbalanced moment, it's apparent in Nioh's side missions, too. It's a shame because the core combat systems they make are really tight and satisfying.
Then again ofc it's kind of subjective what is enjoyable and what is not, I've seen a lot of people saying that the Midir boss fight in Dark Souls 3 is bullshit, but I actually think it's amazing. Same with Armstrong in MGR.
All of that being said, I hope that I will be able to enjoy NG as much as everyone does, because I clearly see the potential. When I give NG Sigma a second chance I'll make sure to dive more into the mechanics in order to understand how to make them click with me.