iPhone -> iPhone 3G "It's only faster data"
iPhone 3G -> iPhone 3GS "It;'s only a better camera"
iPhone 3GS -> iPhone 4 "It's only a new case"
iPhone 4 -> iPhone 4S "It's only Siri"
iPhone 4S -> iPhone 5 "It's only taller"
Every time.
When you iterate a product every year, the changes will not be huge. Look at the car industry. New models every year, a redesign every 5-10 years.
Most people buy a phone every two years because otherwise you will end up paying more to do your 1 year upgrade. The jump from the 4 to 5 will be quite large (Taller screen, much better camera, much faster speed, Siri, thinner, lighter, etc.)
People have selective memory. They remember the dazzling moments from Steve Jobs (iPhone intro, aluminum PowerBook, iPod Nano, etc) but they forget the years of iteration that were done in between. The iPod only had two significant changes, the nano and then the touch. The aluminum PowerBook design did not get redesigned for FIVE years.
It seems more and more these days that Apple fans are expecting Apple to dazzle them with revolutions every single year. Hell, many of the old Macworld keynotes were spent mostly talking about software and not even much hardware. They'd debut a new iLife suite, or iWork. Now Apple fans want a MW07 to happen every time Apple gets on stage.