It appears that X-COM: Enemy Unknown (the new version) is being released on iOS this summer:
I had been contemplating getting it for the Xbox, but I think I'll wait it for it for my iPad. (With young kids in the house it's easier to play an "M" game with an iPad). According to the video it'll be a straight-up port, the only modifications will be for the touch interface.
Loved the original, this is gonna be cool. Just hope it isn't restricted to retina-only iPads.
Greg