What makes a new Apple product evolutionary vs. revolutionary?

I tend to feel that most things in life can be boiled down to a simple algorithm, but I must say I don't understand what the public interprets as an iterative update vs. a revolutionary update.

Lets use the iPad 3 as an example. When it was updated this year, it recieved a 9.7 inch retina display, 1GB of RAM, quad core graphics, LTE, and better cameras. I was blown away by this update, however the general public reaction was "the iPad 3 is only slightly better." Internally, it was a different beast, but externally it looked almost identical to the iPad 2. My friend even asked "How is your new iPad 2.5?"

Lets use the iPhone 5 as an example. It has a larger 4inch screen, LTE, 1GB RAM, A6 processor, and 3-core graphics, thinner, lighter. By all means a very big update, but it looks almost exactly the same as an iPhone 4s, just taller, so the public has generally felt that it is an iterative update.

Look at the iPhone 3GS iPhone 4S, and eventually iPhone 5s. Most people would agree these are in fact iterative updates. Just speed and spec bumps.

Look at the iPhone 4. Now THIS blew people away. Retina display, front facing camera, updated specs across the board. And a brand new look (Sandwhich glass and aluminmum.)

So, if the iPhone 5 had the teardrop shape the Verge speculated a year ago, and EVERYTHING ELSE WAS THE SAME, then it would have been a revolutionary update?

Does it take Specs AND change in facade to make an Apple product revolutionary from a public perception standpoint?

Thoughts?