I'm not really one to judge, because I don't have the sort of literary background to judge but I would say 3.5 out of 5.
Kishi has the best talents in characterization out of the big three IMO, and he has tried to tackle quite complex and mature concepts. However, I think in general he's bitten off more than he can chew, adding many characters that he struggles to keep up with and develop and the concepts he has tried to go into haven't been fleshed out enough because of the flashy plot twists he always loves to produce and time constraints he seems to be under. He also has a bad habit of overplaying the relationships between characters making their relationships seem forced or overly obsessive. However, he writes a very solid story, with great characters and overall plot.