Super Mario 3D Land is the greatest 3D platformer available on handhelds. Ocarina of Time 3D is the greatest adventure game available on handhelds. In the end it all boils down to what genre you favor.
Note that Ocarina of Time will last between 7 to 15 hours depending on how much you care for side quests, exploration and how many times you get stuck (since you haven't played it before). Double this number if you plan to replay the game after unlocking the mirrored world with new level designs and tougher enemies. 3D Land, on the other hand, should guarantee about 9 hours even if you just run through all maps and don't care for the star coins. As you can see one isn't necessarily longer than the other though.
Given your "airplane setting", I'd recommend Zelda. 3D Land is more closely related to smartphone games, so if you're gonna spend hours on a plane you might as well get a more immersive experience.







