Is Ninja Gaiden a good game?

It’s a game franchise that originated in the era of 2D consoles—I’m not sure if it started on the NES or a Sega system. I’ve never played a single Ninja Gaiden game, so I wanted to ask if any of you have—is it actually a good game? Also, which Ninja Gaiden titles have you played? And what is it about? Obviously, it involves a ninja, but what exactly do you have to do?