So I started playing Ninja Gaiden Black today..

Both NG and DMC3 has its flaws and its high points. Just becuase you were expecting it to be like another game you cant let that cloud your judgment on how the game really is otherwise your really missing out on a whole game altogether.
As for me, I liked dmc3 better but I enjoy NG becuase its really fast paced with no slowdown and sometimes you can accidently pull off major attacks without even knowing it. Both of them have their ups ^_^

Jam it back in, in the dark.

Well if you were trying the game out becuase your friends told you that it was better than dmc, then you must have compared it to some extent.
But I agree that each person has different taste, some like ninjas, some like half-deamons. I think some ppl like NG, not just becuase its fast, but becuase they're hardcore fans of the oldies from the genesis days, but of course there are always the doa and shinobi fans as well ^^
I think the only thing I find in common with this is the frustration in difficulty.

There's nowhere I can't reach.