Swordigo is a really impressive venture on iOS. It's a 2D-action platformer with a lot of nice RPG elements. In other words, it's a 2D Legend of Zelda title, and it lives up to that comparison quite well.
There are a few weak points. The graphics aren't exactly impressive though they do get the job done, and the story is barely there and hamstrung by some translation issues, I think. But neither of those things matters much, because the game is well designed. Every swing of your sword pops up XP into a meter, which feels very rewarding and makes the whole affair a lot of fun.
Plus, Swordigo is free today, so you should probably just go download it. It's a quality game anyway, but for zero dollars, it's a must-get.