There are some good things to be said here. A few points in the game, you get the "ninja-y" feel flipping back and forth between pillars and walls. There's a sword and throwing stars, as well as a storyline to go with the boss fights.
Frustrations are many though, the first and foremost being the "sticking" to walls working off-and-on according to the player's intent, as well as partial or full platform jumping controls not landing reasonably well. There's an intentional delay for jumping, which can be gotten used to, but seems an unnecessary feature compared to responsiveness. Hit detection isn't great, you've gotta hit that sweet-spot and erratic enemies are just plain annoying at times. Boss fights a bit absurd for normal player requirements. With saves and cheats, it becomes a bit more interesting than grinding through the choke-points.
For a ninja, Ryu doesn't seem to be doing much sneaking and assassinating. There's no hand-to-hand martial arts, just sword slinging and 'magic' spamming. I realize this is a beloved classic, did enjoy the first level or two back in the day, but am glad to be through with it to satisfy what the full gameplay and story is like. I'll be filing it on the shelf and moving on to better games.