im no Shinobi expert as Ive only played a handful of them, but from reviews Ive read they say it has most commonalities with Shinobi III. As someone who has studied ninjutsu, I see lots of technical errors in the movements of the ninja, but hey Its just a video game so I can overlook those. :P
as for Mario 3D, the first 8 Worlds are sort of a walkover, but the 8 Special Worlds were pretty damn challenging. especially if youre out to collect all star coins. Its really the only 3DS game Ive played so far that plays better with the 3D on.
The thing that sucks with the 3DS tho, is if you accidentally tilt or shift the console while playing, it will throw your view of the 3D off and it can really screw up your concentration often resulting in death, especially with Mario 3D.