Changing the setting to pure sci fi was a huge mistake. Ninja Gaiden always retained a setting that was a cool mix of the traditional and the modern, a ninja with a katana and shuriken and ancient magic fighting against rival ninja clans that used modern weaponry, or a full military force with tanks, helicopters, rockets etc. and then ancient evil fiends getting involved. The setting even veered towards sci fi once with Sky City Tokyo but it felt like a unique take on an idealized future Japanese city that balanced futuristic technology with very traditional Japanese themes. Meanwhile in NG4 you are a Harajuku techwear emo fighting against power rangers with electric laser weapons in a post apocalyptic dead city. It's just too far away from what Ninja Gaiden looks and feels like to me.