First Shinobi game I've played what the 3D version of III for 3DS (lots of 3's), and I thought it was incredible. Now I remember this other original Shinobi game came during the first months of the 3DS, and I recall seeing a lot of people saying good things about it. They were right; this game is great.
I'm very surprised by how good it is. It's just a great platformer/beat em up that's very satisfying and challenging. I'm on level 5 and it has been a blast to play. The presentation makes it look like it was a game originally made for the DS, but it has a nice art-style and the 3D effect is ok.
If you guys don't have it yet, I strongly recommend it. It is dirt cheap ($11) and it is a great addition to the 3DS library.