As someone else already mentioned, iPhone for the average Joe. They're stupid-proof. For a power-user, Android is better. I use Android, but I would recommend iPhone for regular Joes.

If you're the kind of owner that likes to tinker with the device, install all sorts of software under the motto "what happens if I push that button" and if you don't mind flashing/reflashing your phone, then Android is the phone for you.

For everybody else that wants to call people, text/socialize with them, email them, show off where you had your breakfast/lunch/dinner and have some entertainment on the phone with a good battery life, iPhone then. Safe platform to do all of that and it also comes with most stuff you'll want already on it. Blackberry would probably work too but it lacks the bling-blings.

It all comes down to what you want from a smartphone.