Don't get me wrong, this isn't a major nintendo title, but it's actually unique for what it is. nintendo proved they can make different kind of games and still enjoy some success. the campaign mission modes offer a different gameplay then other games bringing back the infamous side scroll (in 3d!). periscope mode is my favorite. allowing you to spin around to find enemy ships and sink them and gives u the ability to dive underwater to avoid enemy torpedos. while it may not be a very high replay value once you beat everything, it does offer a breath of fresh air to the same-o nintendo handheld.
I was skeptical about Steel Diver, but it is a surprisingly good game. I will say that it is very challenging. This is basically a simple submarine simulator. I haven't beaten it yet, but it will give you the feeling of older games. It isn't necessarily long, but you'll probably sink quite a decent amount of time into it because of the challenge. And driving the submarine is pretty fun and has a sort of frantic feel to it as you have to keep all of your controls under control and watch the screen at the same time. I'd definitely recommend at least giving this game a try.