5. Brogue
Brogue is a little known roguelike created by a man named Brian Walker in 2009. As a roguelike, permadeath, ACSII graphics, and turn-based strategy make it a hardcore experience. However, unlike most roguelikes, Brogue sports an intuitive learning curve and an emphasis on making ASCII graphics gorgeous. Originally, the game was available for PC, Mac, and Linux, and it's available for free here.
Since last March, it's also available on iPad for free. As the @ symbol, Brogue tasks players with traversing a 26 floor dungeon to obtain the Amulet of Yendor—a quest that is much more difficult than it sounds. Along the way, mysterious potions, scrolls, and often cursed weapons will assist the little @ symbol towards its goal. Of course, acid jellies, bloat bats, vampires, and dozens of other surprises stand in the way.
Since Brogue features simple controls and menus, moving through the dungeon warrants little trouble; however, the included virtual movement pad could use better hit detection. Be that as it may, Brogue is a hardcore experience, and the best traditional roguelike on iPad.