That stat is pretty out of date by now. Android <= 2 now only accounts for 12% of devices, and most app devs aren't targeting it any more.
And Android might have 5000 devices, but it doesn't have 5000 screen sizes. Still more than Apple has, but hardly 4992 more.
http://www.androidheadlines.com/2014/09/androids-kitkat-clos...
Of course, operating system fragmentation has become less of an issue generally since ICS/JB became dominant.
[0] https://developer.android.com/about/dashboards/index.html?ut...
Most modern phones are 16:9 (720, 960, 1080). There are still a few stragglers (Motorola in particular), but they're becoming a thing of the past.
You basically have three aspect ratios to worry about right now: 16:9, 5:3, and Motorola's 427:240.
With iOS, you have 3:2, 4:3, 71:40 (iPhone 5), and now these new iPhone 6 internal aspect ratios that get hardware resampled.
So, it all boils down to: 4:3 (all iPads) and 1.177 (5, 5S, 5C, 6, 6+).
3:2 is just a legacy ratio that will go away going forward as the 4S gets older. It's not a ratio they have produced iPhones with for several years now.