Cave Story 3D has little playtime (compared to the other games at least) for me for two reasons: I tend to quit playing after 5 minutes because I die every second, and once you finish it in all modes there really isn't much to do except speedrun. No one else that plays on my 3DS ever wants to play Cave Story, so that's probably another reason (I lied!) there isn't a lot of playtime on it. Still one of the best games of all time, though.
Street Fighter also doesn't have much playtime, but that's just because I'm terrible at it (retro and Guy can verify this) - and again because no one else that plays on my 3DS likes Street Fighter.
EDiT: yeah, Steel Diver is a pretty terrible game. It's broken beyond belief. A black spot on the 3DS's otherwise decent catalogue.
This post has been edited by Nathan, Wed, May 30th, 2012 at 13:09