I got this game on launch day, and though I sucked at Ninja Gaiden on normal (never beat it; I'll probably go back and play it on Ninja Dog someday), I decided to try Ninja Gaiden 2 on Path of the Warrior. I got up to Chapter 8 (out of 14), and while I still feel I could've beaten the game on my first playthrough of "Normal" mode, I just got tired of seeing the Game Over screen.
So I restarted the game on Path of the Acolyte, and lemme tell you, if you jump down in difficulty, the game does a fine job of making you feel like less of a man (or less of a gamer, to be more gender friendly). Where once you fought Ninjas there are now a shit ton of bats. Where once you fought a higher-fiend with wings, you now fought one of the easier henchmen that gets its ass kicked easily. Where once you fought a dozen fiends at once, you know fought three or four at a time.
Going from Warrior to Acolyte is a lot like playing Call of Duty 4 on Veteran, or Gears on Insane, or Halo 3 on Legendary, and then jumping down to Normal/Casual/Normal (respectively). Well, actually, not THAT bad, but I have completed 10/14 chapters on Acolyte mode, and I have yet to see a game over screen. Hell, I had so much essence-cash that I was able to purchase all my weapon upgrades halfway through the game and still have plenty left to sit in the bank, whereas on Warrior I was always strapped for cash.
There is one thing Ninja Gaiden 2 has going for it, though: it's still challenging enough to be fun. When I first grabbed Devil May Cry 4, it was the first time I had played a DMC game (sort of: played the first for fifteen minutes). Knowing that the series was supposed to be hard as balls, I started it on Human mode. The game was barely fun enough to keep me playing, and after completion I decided to try Devil Hunter mode with all my gained skills and health from the first play through. NOW I had a challenging and fun, addictive game, but I also can't imagine playing the game without the gained health and abilities that I grabbed from the first playthrough. Ninja Gaiden 2 also allows you to roll your leveled weapons and boosted health to a new game on a harder difficulty, and will probably offer the most pure experience for the game on Warrior, but at least playing through Acolyte isn't going to bore you like Human did with DMC4.