The A4 was not such a big deal. It was mainly a victory in packaging and marketing for Apple.
Performance-wise, the 4 isn't much better than the 3GS, although it's true that it has to power some more pixels.
I still completely understand what you're saying though. The iPhone 4 was on a completely different league and started a new era. Just that build and screen. omg. I think it says it all when the kind of machines needed to build the iPhone 4 were machines that produced low-volume, high precision prototypes. They just had to get many of them.
With that being said though... the iPhone 5 still strikes me as remarkable in ways that the iPhone 4 wasn't.
The advance in packaging is not as big (because there wasn't much room for improving this time around), but it's still a new form factor, with better everything in the inside, while improving the physical characteristics of the thing. Thinner than the 1st and 2nd and 3rd generation iPod touch. Lighter too. Just crazy.
And the performance doubled. From an already fast phone.
New form factor and much better performance is something new in the iPhone world. Never happened before.
A6 (2x CPU and GPU)
Front HD camera
3 mics
1GB of RAM
4G LTE
Dual-band wi-fi
Full sRGB display
It's an at least comparable list.