Ninja Gaiden Sigma 2 or Darksiders??Which should I buy??

[Severance]

^^
so you are basing what you are saying on youtube videos?

as you see all enemies die easily in NG2 they respawn rapidly.
as for Sigma 2 they're tougher and need more tactics to beat them , but don't respawn rapidly, also you NEED those unlimited projectile ammo, why? they don't hurt the enemies at all ! , but they slow them down in order to chain more combos, on NG2 the IS and WS are too freaking powerful.

while you are basing it on youtube videos i am basing it on my own playthrough, NG2 is easier (and a lot more brutal) than NGS2