Aren't into shooters? We've got two world-builders for you.
Call of Duty: Strike Team (iOS)
Call of Duty has already been seen on mobile devices, but Strike Team is the first entry that doesn't deal exclusively with the Zombies mode. Strike Team follows the traditional single-player campaign model, with the key difference of being able to command a squad of soldiers rather than just one. Especially cool is the ability to switch from a top-down tactical view to a first-person view at any time during a mission.
Looking to build words on a mobile device but have difficulty with MineCraft's 3D perspective? Both Terraria and Junk Jack X feature more manageable 2D perspectives. Which one you pick is really dependent on which art style you prefer, though in my time with both, I found myself gravitating towards Junk Jack, which seemed better suited to touch screen controls.