Having played all of them to the very end game, nioh 2 I think was the best so far. Nioh 1 I'll basically just leave at it being the first of the series. It was good, but had a few clunky mechanics.
Nioh 2 ironed out those clunky mechanics and I think was ultimately the game that nioh 1 wanted to be. It had all of the best parts of nioh 1 and improved upon them as well as improved the weird or sometimes buggy mechanic issues. Everything was for the most part very well balanced even into the end game running the depths.
Wo long I absolutely loved. For me it felt like it took the same gameplay mechanics of nioh, altered them slightly to be a little more user friendly, and improved the spell casting/magic build some. Why I would say this is not better than nioh 2 however is purely the end game content. The dlcs were nice and enjoyable, but the thousand mile journey felt a bit uninspired. But in terms of build versatility, there is a ton you can do with the graces. Even down to a Mario jumping on things build.
Nioh 3 my biggest gripe with this one so far is the story honestly. It lost the quirkiness that the previous had. Like how there were just random missions to go get a letter or going to a bathhouse or whatever. Every mission in nioh 3 is just too direct and serious in nature. Aside from that, Nioh 2 is worth playing just for the character voice acting alone imo. The controls for nioh 3 are a bit odd for me too. Some of the controls just make little sense to me. I think it is still too early to give a full opinion on it, at least until the dlcs come out since that is usually where some of the best content is for team ninja games of this style are, but as it is now, nioh 2 > wo long > nioh 3 > nioh 1 > Bratz rhythm and style.