As a kid, these were the fucking tops for me. I played Ninja Gaiden 2 the most, but NG1 was phenomenal as well. I confess, NG3 has always been too difficult to hold my attention. I actually haven't played any of the rebooted games.
I never really understood the game's powerup system. But the jumps were tight, and the sword swing was instantaneous, and the way enemies "popped" when they died was really satisfying.
They did occasionally feel a little cheap with the fucking eagles and bats that seem impossible to track. And the enemy respawn could be unforgiving. Bird bumped you a few feet back? Step forward and it spawns again!
Still, high quality games. I sometimes feel like the only person who really played them. Does anyone else have memories of these?