Ahyes, desktop market more fragmented in device capabilities than iOS :)
- iPhone original, 3G, 3GS, iPod touch 1st, 2nd, 3rd: 3.5' @ 320x480
- iPhone 4, 4S, iPod touch 4th: 3.5' @ 640x960
- iPad original and 1: 9.7' @ 768x1024
- iPad 3: 9.7' @ 1536x2048
Now the funny thing is, on desktops, at least the DPI stay more or less within a range (something around 72DPI to 90DPI). The viewing distance per dot is about the same, so making graphics that work across a huge range of display sizes and the variations of resolution is not that hard. But on iOS devices you jump at the same size display to 2x the DPI count, which is kind of jarring to support.