You can't compare Android with hardware as Android is an operating system while iPhone is hardware. But there IS a distinct change from donut to jelly bean. In fact jelly bean blows any version older than 2.3 out of the water...
The BlackBerry hasn't changed much either but I can hardly call them perfect from the beginning, either. Their market is similar to Apple's in catering to those who are resistant to change, or, going with the car comparison, prefer a carburetor and rear-wheel drive over a fancy car with fuel injection and traction control and airbags....and let's face it, RIM is dying...they coined the term 'battery pull' as their OS had a bad habit of locking up for no logical reason...