It is sad not having the original SimCity on something like the iPad. The version they offer is some abomination trying to be FarmVille begging for cash at every turn.
It would be theoretically and easily possible, but legally impossible to port the original C version of SimCity released under GPLv3 (called "Micropolis") to the iPad, because of the anti-Tivoization clause, it's a violation of the GPLv3 to put it on the Apple app store.
https://en.wikipedia.org/wiki/Tivoization
https://apple.stackexchange.com/questions/6109/is-it-possibl...
https://github.com/SimHacker/micropolis
However there's nothing stopping you from running one of the versions of Micropolis that's been rewritten in JavaScript to run in the web browser (because it's distributed via the web instead of on the App store), or contributing to those projects to make it run well on the iPad.