It should be noted Apple is still dominating the app sales charts among all mobile store platforms. In 2010, the Apple App Store was worth $1.7 billion while the Google Android Market stood at only $102 million.^1 Consider also that the number of apps in the Android market will likely surpass the number of apps in the Apple app store later this year.^2 For any given single app you create, publishing it for the Apple platform seems to net you access to an order of magnitude greater market share than any other mobile alternative.
About a month ago I decided I wanted to get serious about making a game -- and decided on the iPhone platform partly because of the above.
Take a look at this TechCrunch article. It's a year old, but I think its still valid. In my experience, it is easy to recover your developer license fee, but as you can see in the table of the article, the worst performing devs earn less than 20$ in almost a year. Keep in mind that Apple will transfer your proceeds when you have earned at least 150$ per region or something like that.
I'm under the impression that you can, if you jailbreak.
Could be dated, though.
There's 2 options that I know of.
You've got Phonegap which, to my knowledge is pretty much what you're asking for. A wrapper of sorts for a web application written in HTML and JavaScript. It's got some good documentation and so far as I know is released under the MIT License.
Then you've got Titanium Appcelerator which is sort of the same thing though it can support php, official release last time I checked did not though some people have gotten it to work. And as I understand it, it compiles to an actual native executable with a native UI and all.
Though form personal experience the documentation is horrible unless you're willing to pay a LOT of cash to get access to their developer network.
It's not clear whether you're referring to the tools used to create the graphics, or whether you're referring to the library used to display them on the iOS device screen. Which do you mean?
If the former, there are literally hundreds of apps, and the one you choose depends on the type of graphics you want to create. For instance, 3D modeling will require something like Maya, photographic manipulation might imply Photoshop or Pixelmator, and cartoon illustrations might fall under Flash.
As far as programming these graphics, again, it depends. If you're looking to do Angry Birds or Burn the Rope, a fantastic choice is Cocos2d for iPhone. It's easy to get up and running with, has a large community, and lots of sample code. If you need 3D, you're looking at a higher learning curve with OpenGL ES, or perhaps you could use a dev tool like Unity.
Good luck in your project.
I started working with iOS a few years ago too, although I didn't have the Cocoa background. I've been trying to compile lists of useful frameworks/libraries and other resources on Convore.