The only game I really play on iOS is Dominations.
Typical F2P, but unlike so many other games in that genre, it's very well balanced, no comic style, battery saving 2D isometric view, includes some interesting historic backgrounds, although the game itself isn't historically accurate of course.
There's no need to invest money and those people who invest money will level up a little quicker, but in battles you're always matched according your level, so there's no classic pay2win.
Also, I think there's a full version of Tropico released of iOS, but never played that...