I'm actually working on an iOS project in my spare time but I'm having a hard time figuring which one of these program I should be using for it. Personnaly, I'm much more experienced with Photoshop since I'm a freelancer/webdesigner but I think Illustrator could be pretty helpful in this situation for all the retina and multiple resolution support (iPhone/iPad2). Can't tell you much about my project but we're working on a 2D action game with graphics similar to angry birds and such. (colorful and quite simple). Based on your own experience, what would you suggest me to use to work this aspect? I'd definitly prefer Photoshop but I'm afraid I would have to work twice as much to get the job done if I have to do it all over again for the resolution! =/ Actually, I'm thinking about working on the graphics based on the iPhone 4 resolution (retina support) to make sure it can work on both devices (iPod Touch, iPhone) and maybe iPad.. anyway! I'm feeling a bit lost in all this, I cleary need some advice!=S

Hum.. if it can help, we're working to achiev this kind of visual art for our games, you can see this as a reference: http://www.droid-life.com/wp-content/uploads/2011/03/angry-birds-st-pattys2.png

[font=arial, verdana, tahoma, sans-serif][size=2]Hard to say. That's like apples and oranges. Ones vector and ones raster. If you are working on flash games the you may prefer Illustrator. Photoshop is great for creating textures though.
If I had to pick only one, It'd be Photoshop for sure.[/font]

Grab Illustrator, and use Photoshop Elements, which is dead cheap, and more than good enough.